Restructured mesh classes a bit.

Now there is the basic MeshInterface (just Format, buffer type, vCount and prim type).
Then MeshBase extends MeshInterface with a single VBO id and bindings cache. Then Mesh and MeshIndexed extend MeshBase to provide differents APIs to that single VBO.
Next step: implement a class that extends MeshInterface that uses one VBO/format, and one draw call/format,shader. More info: glMultiDrawArraysIndirect (multi draw + instancing).
Renamed mesh classes
Added MeshBatched (WIP) to use glMultiDrawArraysIndirect
Implement vsync on Android
Done grouping (several meshes on VBO). Class MeshBatched is usable in place of traditional mesh. Still have to implement the actual batching and batch submission, plus the per-draw data attribute.
Merge branch 'master' of github.com:Towerthousand/VBE
Reimplemented allocator correctly for MeshBatched::Buffer
Added ivec3 uniform suppor. Added MultiDrawIndirect support on MeshBatched. Added GLEW in place of standard GL/gl.h (only when using SDL2). Added a instanced attribute hack to have a drawID as a vertex input when using MultiDrawIndirect. The name of this attribute is hardcoded for now: draw_index
Erased 'unused' warning
Fixed un frustum constness and improved MeshBatched pow()
Merge https://github.com/Dirbaio/VBE
Merge branch 'master' of https://github.com/Dirbaio/VBE
fixed mesh obj loading
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