game_engine. Change engine object creation interface.

Separate object creation from render creation.
Change the create object method not to create the render.
Add a create render method to engine.
For now only creates render on the root object.
Update test game to create a render on the game root object.
Fixes to doxygen comments.
Add a convenience shared ludus object pointer.
game_engine. Create SLES audio buffer.

Change base audio buffer to a virtual class, with no data.
Create an SLES buffer that holds SLES audio data - raw buffer data, and buffer size.
game_engine. Add deleter function to audio buffer.
game_engine. Add audio buffer manager.

Add base buffer manager to internal audio.
Add SLES buffer manager.
The current implementation creates an audio buffer with null data.