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).
A general speedup should be apparent, with even more peformance increase when compiling optimized.
WARNING: Tested and it seems to work, but if something breaks, please report.
-Added Navigation & NavigationPolygon nodes
-Added corresponding visual editor
-New pathfinding algorithm is modern and fast!
-Similar API to 3D Pathfinding (more coherent)
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-Moved drawing code to a single function that takes linked list (should make it easier to optimize in the future).
-Implemented Z ordering of 2D nodes. Node2D and those that inherit have a visibility/Z property that affects drawing order (besides the tree order)
-Removed OpenGL ES 1.x support. Good riddance!
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-Ability to set 2D nodes as bones
-Abity to set 2D nodes as IK chains
-2D IK Solver
-Improvements in the UI for adding keyframes (separate loc,rot,scale buttons)
-IMA-ADPCM support for samples, this means that sound effects can be compressed and use 4 timess less RAM.
-New 3D import workflow based on Wavefront OBJ. Import single objects as mesh resources instead of full scenes. Many people prefers to work this way. Just like the rest of the imported resources, these are updated in realtime if modified externally.
-Mesh resources now support naming surfaces. This helps reimporting to identify which user-created materials must be kept.
-Several fixes and improvements to SurfaceTool.
-Anti Aliasing added to WorldEnvironment effects (using FXAA)
-2D Physics bodies (RigidBody, KinematicBody, etc), Raycasts, Tilemap, etc support collision layers. This makes easy to group which objects collide against which.
-2D Trigger shapes can now also trigger collision reporting in other 2D bodies (it used to be in Area2D before)
-Viewport render target textures can now be filtered.
-Few fixes in GDscript make it easier to work with static functions and class members.
-Several and many bugfixes.
