Changed the mesh and lua samples to load from a scene file.
Changed GP_ERROR on windows so that it will break properly when in debug mode.
Changed Material::create to return NULL if there is an error instead of failing hard. Also fixes loading a GPB with unused materials.
Merge branch 'next' of https://github.com/blackberry/GamePlay into next
Merge pull request #1242 from dgough/next

Changed mesh and lua samples to load from a scene file