pingo. Minor fixes to geometry manager.

Pass resource manager to resource manager constructor by reference.
Add doxygen comment to resource manager deleter arguments.
audio. First step in loading audio assets into audio buffers.

Add the resoruce manager as a field of the SLES buffer manager.
Add methods to SLES buffer manager to create an SLES player that decodes audio assets into buffers.
This is just a preparation step, asset loading is not implemented yet.