* Solve bug related to corrupted texture tiles for certain sizes.

* Regard layer settings when sampling height map.

* Make Tile in to a class instead of a struct.

* Memory aware lru cache. Needs cleanup.

* Clean up and comment.

* Clean up and comment.

* Clean up

* Clean up and comment.

* Fix compilation error on Windows.

* Specify data type explicitly in GDAL xml config files for Utah height maps. Closes #242

* Update the key type for the memory aware lru cache and use a unordered map instead of a map.

* Solve pixel row size bug.

* Solve initialization bug.

* Add cache size as property of the globe browsing module.

* Use memory aware tile cache for text tile provider.

* Log GDAL errors as GHOUL messages

* Add the ability to toggle tile level limiting by available data

* Add ability to toggle GDAL logging

* Add lock guard to memory aware tile cache

* create base class rawtiledatareader that can be extended with different implementations than GDAL.

* Let GdalWrapper take care of global GDAL settings.

* Move iodescription to separate file

* Move some functionality from gdalrawtiledatareader to rawtiledatareader

* Move functionality from gdalrawtiledatareader to rawtiledatareader.

* GDAL is no longer a necessary dependency for the globebrowsing module. However to read tiles, the SimpleRawTileDataReader needs to be implemented. Otherwise GDAL is needed.

* Add ifdef check for GLOBEBROWSING_USE_GDAL

* Implement SimpleRawTileDataReader. Currently can only read pow 2 textures.

* Change ints to unsigned long longs

* Limit number of texture creations per tile provider per frame

* Solve linker error on windows

* Fix Windows build errors

* Fix crash in reading local patches

* Update lodglobe descriptions

* Abstract away overviews in gdal raw tile data reader

* Update Mars and Moon configs.

* Update screenshot script

* Update ghoul version

* Remove use of interaction depth below ellipsoid

* Normalize direction vector

* Use scale for distance swotch

* Go back to use of interaction depth below ellipsoid

* Fix comments on pull request.

* TileProviderByLevel error does not propagate up.

* Comment on mars and moon mod file

* Add model space cut off level as a property

* Update ChunkTile struct

* Minor clean up

* Go back tu constructor for ChunkTile

* Initial restructuring of the Globebrowsing branch

* Update Ghoul repository
Fix include guards

* More cleanup

* Split texttileprovider subclasses into separate files

* Move TileProviders into namespace

* Convert static class methods into free functions

* Splitting tile subclasses into their own files
Remove `using namespace` from header file

* Split TileDataSet subclass into separate file
Update SGCT reference

* Move shader preprocessing data into internal class

* More Globebrowsing cleanup

* More cleanup
Remove unused Convexhull class

Update Ghoul repository
Remove libgdal link

Cleanup of include guards in modules

Add documentation to ScreenSpaceRenderable
Add documentation to Ephemeris
Add documentation to Rotation

Update SceneGraphNode to contain rotation information and remove rotation definition from renderable model.

Solve bug that cause some vertices to be misplaced in MultiModelGeometry and calculate MVP matrix for renderable model in double precision

Update Ghoul repository

Renamed SceneGraph to Scene
Added new class SceneGraph to handle scenegraph related tasks

SPICE-time dependency, retrieval of spice ephemerides and rotational matrix + coordinate references.

Added functionality:
- New class renderablesphericalgrid is repurposed code from powerscaledsphere class.
  Due to z-buffer issues used as reference grid to confirm planetary orbits are correct.
  This has been a major problem as prior we had no visual reference.
  Now we have a Galactic-, Celestial- and Ecliptic-coordinate grid.
  To this also added separate shader: grid_vs.glsl / grid_fs.glsl
  These grids have a static-rotational matrix derived from partiview (thanks to Brian)
  since spice req. to-from frame to compute rotational matrix.

Time dependency:
- Added struct RuntimeData - which for now only contains openspace time and is passed to all renderables
- All renderables accept runtimeData, keep private reference and use for computation of rotational matrix
- This obviously carries corresponding changes to Scenegraph and ScenegraphNode.

Spicemanager:
- Added function that more easily provides access to rotational matrix used in spice
 (used in renderableplanet for computing planetary objects spin around axis)

Ephemeris-classes:
- Now compute ephemeris from spice based on timeepoch in runtimedata
  TODO: once z-buffer fixed - set ephemeris correctly as meters (not kilometers)

Renderengine:
- Advances time with the advanceTime method in RuntimeData struct

ISSUES:
- Our Y axis NOT same as SPICE or star-catalogue, all renderables rotated now 90deg, needs redefinition,
  lots of debugging and major headaches before this conclusion.
- Depth buffer needs to be fixed in order to properly place planets.
- Spice kernels have finite time-range, when time stops - simulation ends - ugly fix: reset time to zero.
  Possible fix: kernels de431 (part 1-2) cover huge timespan and most likely have functions to extrapolate time,
  drawback is that they are 1,7 gb each.

TODO:
- Compute and draw dynamic ephemeries for each renderable. Either do full year sweep then update for each point or
  create a tail of linesegments for each planet. Dont know yet how to do this, would like spicephemeris to be
  sub-class of Renderable (have own render() method) - good/bad?

- Moved all OpenSpace headers to separate include directory
- Added OpenSpaceTests binary with OPENSPACE_HAVE_TESTS define
- Added CMake setting of BASE_DIR
- Added OpenSpace initial tests for SceneGraph and SceneGraphNodes
- Added OpenSpace initial tests for psc and pss
- Restructured OpenSpace so no GL functions are called in constructors
to make the classes testable

- Todo: Make the base dir possible to set through command line argument
and configuration file

added OpenSpaceEngine
added ConfigurationManager
added query functions
removed GLEW-related Windows warning
added old external control classes
more restructuring