Changed link hirarchy to have math as base

Changed link hirarchy to have math as base, useable by src/util.
    README.md
    common_build.py
    src/Android.mk
    src/SConscript
    src/SConscript_tests
FileUtil use SDL instead of boost filesystem

FileUtil use SDL instead of boost filesystem
    src/util/Asset.h
    src/util/FileUtil.cpp
    src/util/SDL.h
    src/util/TestFileUtil.h
Ported more sdl2-gamedev src/util classes

Ported more sdl2-gamedev src/util classes
    src/util/CharMap.cpp          (+)
    src/util/CharMap.h            (+)
    src/util/File.cpp             (+)
    src/util/File.h               (+)
    src/util/FileMonitor.cpp      (+)
    src/util/FileMonitor.h        (+)
    src/util/TestCharMap.h        (+)
    src/util/TestFile.h           (+)
    src/util/TestFileMonitor.h    (+)
    src/util/TestTimedExecution.h (+)
    src/util/TextBoxText.cpp      (+)
    src/util/TextBoxText.h        (+)
    src/util/TimedExecution.cpp   (+)
    src/util/TimedExecution.h     (+)
Ported src/extern from sdl2-gamedev

Ported src/extern from sdl2-gamedev
    src/extern/CObjUtil.cpp        (+)
    src/extern/CObjUtil.h          (+)
    src/extern/tiny_obj_loader.cpp (+)
    src/extern/tiny_obj_loader.h   (+)
Ported graphics/GlState

Ported graphics/GlState
    src/graphics/GlState.cpp (+)
    src/graphics/GlState.h   (+)
Added ImageResouceManager and Surface classes

Added ImageResouceManager and Surface classes
    src/graphics/ImageResourceManager.cpp (+)
    src/graphics/ImageResourceManager.h   (+)
    src/graphics/Surface.cpp              (+)
    src/graphics/Surface.h                (+)
Ported graphics/GlUtil

Ported graphics/GlUtil
    src/graphics/GlUtil.h   (+)
Ported graphics/{MeshResourceManager,Mesh}

Ported graphics/{MeshResourceManager,Mesh}

    src/graphics/Mesh.cpp                (+)
    src/graphics/Mesh.h                  (+)
    src/graphics/MeshResourceManager.cpp (+)
    src/graphics/MeshResourceManager.h   (+)
Ported graphics/{ShaderProgram,ShaderUtil}

Ported graphics/{ShaderProgram,ShaderUtil}
    src/graphics/ShaderProgram.cpp (+)
    src/graphics/ShaderProgram.h   (+)
    src/graphics/ShaderUtil.cpp    (+)
    src/graphics/ShaderUtil.h      (+)
Added graphics/ShaderResourceManager

Added graphics/ShaderResourceManager
    src/graphics/ShaderResourceManager.cpp (+)
    src/graphics/ShaderResourceManager.h   (+)
Added core/ResourceManager

Added core/ResourceManager
Convenience class for resource management

    src/core/ResourceManager.cpp (+)
    src/core/ResourceManager.h   (+)
Misc fixes, changes

Added missing port of GlUtil.cpp
Define of USE_OPENGLES at appropriate place
Added test of GlState and removed TestEmpty

    src/graphics/GlUtil.cpp    (+)
    src/graphics/SDL_opengl.h
    src/graphics/TestEmpty.h   (-)
    src/graphics/TestGlState.h (+)