A wrapper around an OpenGL texture handle which is being handled (allocated, freed,
drawn into, data loaded onto, etc...) by another class. ExternalTextureProjected2D
simply allows the projection capabilities of TextureProjected2D to be applied
to such an externally handled texture.
Resizes this two dimensional texture to the given new size. This deallocates
any data stored on the graphics card and dirties the texture.
If the texture size has been made larger, setData( ) or mutate( ) should be
used to provide data for the new larger sections of the data. The dimensions
of the data array argument to set data should be float[dataSizeX][dataSizeY].