fixed: TODOs, memory management (ref-count with autorelease pool), move code into proper packages

fixed: TODOs, memory management
add initial gradle script (to build libnst manually)

PY-21979: IDEA-CR-30103 update env variables in Django console, return False in python code explicitly

After the change the reference could be resolved to a class only if it
is a part on fqn. This case is handled before resolver processor is even
created.

"isPackage" has broad semantic: there are cython packages, stubs etc,
but for PySymbolFieldWithBrowseButton we only need source packages.
No need to export it on extension level.