Initial changes to support a shared context in flash mode
Don't alter the stage when using a shared context
Initial changes to support a shared context in HTML mode

At the moment the shared flag has no effect, but a context can be passed in.
Fix initialising a Flash stage when no context is given
Added a method to Texture to get the bounds of an area matching a color

Behaves similarly to BitmapData#getColorBoundsRect
(http://help.adobe.com/en_US/as2/reference/flashlite/WS5F7E996C-A0F6-4d89-BC17-69622D209F21.html).