Minor cleanup: TestAsset.h

Minor cleanup: TestAsset.h
    src/util/TestAsset.h
Isolated FileInfo::TYPE_{ASSET,WRITABLE} to FileUtil

Isolated FileInfo::TYPE_{ASSET,WRITABLE} to FileUtil

Before, Asset class used to know OS filesystem specific details. This shouldn't
be the case, as the Asset class simply represents an asset object. If android
and linux read this differently, it should only need to be differentiated in the
FileUtil and File classes.

    src/audio/AudioResourceManager.cpp
    src/audio/MusicTrack.cpp
    src/audio/SoundChunk.cpp
    src/graphics/Mesh.cpp
    src/graphics/MeshResourceManager.cpp
    src/graphics/ShaderProgram.cpp
    src/graphics/ShaderResourceManager.cpp
    src/graphics/ShaderUtil.cpp
    src/graphics/ShaderUtil.h
    src/graphics/Surface.cpp
    src/util/Asset.cpp
    src/util/Asset.h
    src/util/File.cpp
    src/util/File.h
    src/util/FileUtil.cpp
    src/util/FileUtil.h
    src/util/ObjUtil.cpp
    src/util/TestAsset.h
    src/util/TestFile.h
    src/util/TestObjUtil.h
Added information about preference (INFO) format

Added information about preference (INFO) format
Also provides link to emacs major-mode

    README.md