Google+ plugin: url encoding for redirect solved

Not sure if this is all that is needed for the fix.
Also did not pay attention to possible tests...

This fixes a redirect error while adding a new user for the GooglePlus plugin.
The plus sign in the url (%2b) gets urlencoded twice, which causes a wrong redirect from google.

The uri called is /account/?p=google%252b, because the % is url encoded.