Added KeyframeMesh::Get/Set vertex components
Fixed ShaderBuilder requirement
Constant buffer mapping returns non-const pointer
Fixed warning
Fixed keyframe normal/tangent interpolation
Removed todo comment
Improved KeyframeMesh AABB support

When you use KeyframeMesh::SetPosition(frame, vertex, pos), it will now
invalidate the frame AABB.
Finish() method will now generate automatically invalid AABBs before
interpolating
Added BufferMapper class

Used to map/unmap a buffer automatically and provide a RAII
exception-safe class
(Rect|Cube) Fixed ExtendTo method (Close #6)
Added VertexMapper
Added DebugDrawer::DrawNormals(submesh)
Made use of BufferMapper