obsfate: filter out current user if not in verbose Obsolescence is sometimes used only locally so the obs-marker users is always the same. Showing the user in this case does not bring much values. In the case where multiple users rewrite the commit, display the full list of users. Also show all users in verbose mode.

ui: add the possibility to returns None as username in ui In a later patch we want to retrieve the current username or None if it isn't defined. Add the acceptempty parameter instead of catching Abort.

test: test obfate template keyword in test-obsmarker-template.t These test updates are pretty big by themselves so put it in a separate patch for easing the review process.