Add empty constructor for empty Mesh
Remove predefined vertex attributes. Now all elements are specified by string.
Fix crash due to weird mouse button returned when two-finger scrolling on a touchpad. No idea what causes this.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	include/VBE/graphics/Mesh.hpp
	include/VBE/graphics/MeshBase.hpp
	include/VBE/graphics/MeshIndexed.hpp
	src/VBE/graphics/Mesh.cpp
	src/VBE/graphics/MeshBase.cpp
	src/VBE/graphics/MeshIndexed.cpp
Merge pull request #3 from Dirbaio/master

Some things