Add Sphere class
Add Shape class
Shape & Mesh: Move lots of Mesh functionality to Shape
README.md: Update goals statements
Merge branch 'develop-0.1.x' into develop-0.2.0

Conflicts:
	include/bakge/Bakge.h
	include/bakge/graphics/Mesh.h
	src/graphics/Mesh.cpp

Also update code using triangles to use indices instead