Add the ability to pass a boolean value into the require function that gets passed into the loaded asset as a `enabled` property

Globally rename OpenSpace Helper to OpenSpace_Helper to remove space in the application name.  Also removes need for CMake CMP0037 (closes #2119)

Request the current version later in the initialization after the operating system has been detected (#2186)

* Remove planet geometry and simplespheregeometry
* Fix RenderablePlanetProjection specification

And update tests that use the conversion

Fixes lost precision when printing navigation state from openspace.navigation.getNavigationState()

Note that the anchor should be used as a reference frame per default. Also, it should always be used, if possible. We have quite some problems when using other reference frames

PR: #2175

Horizons unit tests

Add asset for Shepherd moon group of Saturn system

Add Itokawa asset

and throw warning if setting to non-existing node

* Trail and model

Add enable/disable property for TimelineRotation

Add settings in OpenSpaceEngine that sets visibility in gui

Add gamma correction property to Screen Space Renderables

When converting profile version 1.0 to 1.1 also convert the naming of the keypad numbers (closes #2138)

Fix filename when downloading multiple files in urlsync