GitHub users! Create accounts for GitHub users so they can eventually modify their addons.

These changes work together with the socialadmin and githubauth plugins. If those are not active, there is no login possible with a GitHub account, which makes the changes more or less useless. For githubauth, a GitHub API application needs to be created and set in the plugin config.

Mind that those plugins are made for Habari 0.10 and might need changes. There is already a 0.9 branch for the socialadmin plugin.

More thoughts:

* What about contributors other than the original author?
* Notify plugin authors they can now login?