Re-added SQL setup script with fail-safe functionality.

SQL will now work even if the DB and user already exist.
Added new GPlusBot which will interface with Google+ Pages
SocialCenter updated to support Google+ as well.
Endpoints defined for Google+ OAuth handling
Added missing GPlusBot import into SocialCenter
Fixed incorrect endpoint definitions for Google+ authentication
Updated view with login/logout link for Google+
Implemented user authentication logic for Google+
Fully implemented client token exchange for Google+

Workaround is used, as Buffer does not properly follow the OAuth 2.0 specifications.