Add logic to login againt FAS-OpenID

This code allows to retrieve an API token from the tagger API, this way later we can
authenticate the user performing the actions.
Update URL to the new names scheme

The API on the website has moved to /api/ in the auth branch which will land once the
new python-fedora-flask is released and brings in the FAS-OpenID flask plugin
Set the window logo and fix a missing comma
Handle situations where the server is not accessible

In this case the application pops-up an error window with the error message.
Add __version__ information
pep8 cleanup
Flag error message as being an error (red font)
Structure the sources

- Create a gnometagger module containing the gnome-tagger app
- Move the data (.ui and .png) into a subfolder
Fix import the data files (.ui and .png) from another location than gnometagger
Add auth and simplify voting code

- Add auth information for requests that vote or add tag
- Split the vote callbacks by using one method to perform the action
using a different parameter according to the action performed
- Fix call to retrieve the API token