Texture: No way to update existing texels #27
Description
Texture is currently lacking a method to update a region of existing texels. This is normally done using glTexSubImage.
On a related note, Texture::submit always calls glTexImage. The recommended practice is to configure the texels once with glTexImage and then call glTexSubImage to update them. See http://www.opengl.org/wiki/Common_Mistakes#Updating_a_texture.