We are disabling the plugins on upgrade and emailing admins
about this if they have a plugin configured.
This is required because OAuth 2 credentials are now required
in the plugin configuration.
NOTE: These strings are temporary and need to be improved.
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.
