Allow blank usernames on the jsconnect plugin.

This is just a checkout of stage in case we want to launch early.
Merge pull request #167 from vanilla/hotfix/jsconnect-blank-username

Allow blank usernames on the jsconnect plugin.
Merge branch 'master' of github.com:vanilla/addons
Add a config setting to allow forums to not use google+ avatars.
Merge branch 'feature/google-plus-avatar-setting' of github.com:vanilla/addons into stage