-Scene edit state is saved outside the scene now, to avoid changes .tscn files when nothing really changed
-Created a VariantWriter helper to unify all variant to text writing
-Moved SceneFormatText writing to VariantWriter
-Moved ConfigFile to use VariantWriter and VariantParser, added compatibility mode for old .cfg files that use engine.cfg format
All classes were reviewed apart from VisualServer for which no argument name is documented at all.
While doing this review, I found quite a few bugs that were fixed either in earlier commits or this one (mostly documentation bugs though, i.e. some arguments were listed at the wrong place).
-Fixed many bugs in stretch mode
-Fixes to camera project and unproject as consequence of the above
-added setget to script (documented in script doc)
-more fixes to collada exporter for blender
