Update core (repository & portfolio) to use autoload facilities,
getting rid of not-needed-anymore requires.
Clarify a bit the readme_moodle information and expected use.
Updated the various plugins to use OAuth 2.0 for authentication
against google apis. Google are phasing out AuthSub and pushing OAuth as
the replacement.
This changes repository_googledocs, repository_picasa,
portfolio_googledocs and portfolio_picasa
The token for requests is now stored in session rather than a user
prefence and it persists less but doesn't bother the user more than
necessary.
The google docs portfolio plugin is converted to use resumable upload
API as this appears to be what Google have replaced this with.
Unfortunately unlike authsub OAuth will require some setup by admins,
this is linked as a docs page.
1. Added tracker issue number in comment
2. Fixed stored_file::delete_reference()
3. repository::send_file() will throw exception if not implemented by subclass
4. Fixed renaming unit test, added one unit test for deleting original file
5. Fixed copyright statement for googledoc and picasa repository plugin
6. Implemented stored_file::set_filesize()
