[MMc] OpenHeist Object Rendering Complete

Object rendering is now complete in OpenHeist. This allows for a full scene graph, player and non-player characters, zOrder sorting, and non-character objects. The Luxembourg example game takes advantage of the non-rotating animation option to keep the heads upright as the character direction arrows spin:

I also added a sprite debugging view, which is enabled by default in Luxembourg and can be toggled from the GApp::debugWindow (push F11, and then the icon with the switches to access this). It dims the screen 50% and then draws an overlay of the bounding box and coordinate system for each heist::client::Object:

I'm going to tidy up a few more features for object rendering and then move on to the map. The documentation has been updated to include more information about the coordinate system. The key points are:

• Everything is scaled to render as if the screen were 1920x1080
• 96 texels per "meter" (blocks will be one "meter" in the map)

The online documentation is fairly out of date at this point, so be sure to build the local documentation using Doxygen from the library source code.