Merge pull request #1417 from mbebenita/nat

Show multiple backends side by side in the inspector.
Merge pull request #1418 from mbebenita/nat

Only collect timeline profiles when the profiler is active.
Cleanup
Correct guard in Shumway.Player.leaveTimeline
Lazily create backing buffers in Shumway.Tools.Profiler.TimelineBuffer

Prevents allocation of more than 48MB during startup.
Merge pull request #1419 from tschneidereit/nat

Lazify TimelineBuffer backing buffer creation
Initialize TimelineBuffers when reset() or createSnapshop() are called.
Keep back references in renderables so that referrers can be invalidated if renderables are invalidated.
Make RenderableShapes dynamic if they have textures.

The textures may not be loaded when shapes are constructed. This means we need to invalidate the cached shapes on the GPU if textures are loaded at a later point.
Remove alpha property from Frames and only deal with ColorMatrices.