Project bot (Fix #332)

The intention here is to
* Create an "edit bot" account that has at least "push rights" (e.g. a GitHub "collaborator") to the given project to perform a specific action on the behalf of an, otherwise non authenticated, user.

I *think* it requires an account with "admin" permissions to get a list of authenticated users for a given project, so I decided to take a more "hackier" approach:

1. Try to perform the action on behalf of the current logged in user and if this "fails"<br />
1a. Try to perform the action on behalf of a configured "edit bot"

When the status changes (`open` <=> `closed`) a comment will be generated that includes the username of the user that performed the action.

This should be carefully reviewed and tested (how?) before merging into master. :wink: