Make RefCounted heap-phobic

Reference counted classes' constructors are no longer required to be
protected, thus allowing direct stack and member construction of such
classes.
Export plugin interface accessors unmangled

Also add platform macro for Mac.
Remove MeshStorage
Remove MeshStorage [2]
Make SpriteBatch work with no material assigned

Presume texture size to be 1×1.
Enhance importer and exporter interfaces

The virtual destructor is already provided by RefCounted.
Move member-function bodies out of ShaderProgram class definition
Add quasicrystal sprites

Also remove SDL from the Universe.
GeometryBuffer stub

Very likely to be rewritten from scratch soon.
Add MaterialParameter, unsafe for now
Update projects