Implemented mesh primitives in Framework, and set up Application Main to fill the PrimitivesManager in MeshManager with the default primitives currently implemented in Framework.

MeshManager will now look at the PrimitivesManager as a third option during get_or_create, after the TemplateManager, to promote the ability to "override" any primitive with a custom implementation.

The TriangleSample still show how to set up a triangle mesh from scratch in gm-engine.

The PrimitivesManager is set up such that new primitives can be added to it externally, and Mesh Manager expose an add_primitive interface, similar to how TemplateManagers expose the add_templates interface.

I also renamed all name definitions for properties and components to hold a GM_ prefix to make it easier to look up all gm-engine definitions.
Merge branch 'master' of https://github.com/eoma/gm-engine