Maintenance, Bugfixes and Tweaks
#ADD: ContentProvider.GetAvailableContent now allows an optional baseDirectory parameter.
#CHANGE: Added some files and folders to the .gitignore list
#CHANGE: When the editor crashes during plugin reload, it will backup the old logfile before overwriting it.
#FIX: Fixed wrong VisibilityFlag behavior in Renderer class that caused ScreenOverlays to ignore all other Group flags.
#FIX: Fixed TextRenderer not updating immediately in the editor when assigning new Fonts.
#FIX: Fixed editor startup failing completely when an Assembly that is referenced by a CorePlugin doesn't exist.