Adds missing notices, and ensures all the notices are consistent. The Cogl
blurb also now reads:
* Cogl
*
* An object oriented GL/GLES Abstraction/Utility Layer
For the asynchronous loading we need a function call that parses
a file, given its path, and retrieves the image width and height.
This commit adds cogl_bitmap_get_size_from_file() to the CoglBitmap
API.
