[Toolkit.Game] Improved SharpDXElement to avoid memory leaks and to make element reusable between multiple Load/Unload calls.
[Toolkit] Fixes to ModelCompiler and preparation of data structures

Conflicts:
	Source/Toolkit/SharpDX.Toolkit.Graphics/SharpDX.Toolkit.Graphics.csproj
	Source/Toolkit/SharpDX.Toolkit/Graphics/ModelData.cs
[Toolkit] First pass on model animation
[Toolkit] Changed keyframes to SrtTransforms and added linear keyframe reduction
[Toolkit] Forced ModelCompiler to collect all bones for now, and updated data structures
[Toolkit] More documentation and cleanup.
[Toolkit.Compiler] Bounding spheres of skinned meshes are now calculated in mesh space (in default pose), instead of bone space.
[Toolkit] Renamed SrtTransform to CompositeTransform
[Toolkit.Compiler] Fixed bind transforms for meshes that have additional tranformations in bind pose
[Toolkit.Compiler] Create bones before referencing them, while creating meshes
[Toolkit.Compiler] Fixed bind transform calculation. (This is unwieldy, since Assimp does not provide the actual bind pose)
[Toolkit.Game] Added AnimationSystem

Conflicts:
	Source/Toolkit/SharpDX.Toolkit.Game/SharpDX.Toolkit.Game.csproj
[Toolkit.Compiler] Added check for non-existing collections
[Toolkit.Compiler] Revert to using offset matrices, as "improvised" bind poses didn't achieve the actual intent to
1. Effortlessly support additive animations
2. Share skinning matrices between multiple models

Conflicts:
	Source/Toolkit/SharpDX.Toolkit/Graphics/ModelData.cs
[Toolkit] Updated license date

Conflicts:
	Source/Toolkit/SharpDX.Toolkit/Graphics/ModelData.cs
[Toolkit.Graphics] Added selector for depth-stencil subresources
[Toolkit.Graphics] Fixed size calculation for multisampled TextureView (issue #425)
[SharpDX] Revised Quaternion, Matrix3x3 and Matrix LookAt and Billboard methods
[SharpDX] Restored Quaternion.RotationLookAtRH/LH
[Toolkit.Game] Fixed merge conflict (#380).