Add login to frontend

1. Click login button
2. Be taken to login form
3. Enter credentials
4. Get key, save it
5. Button changes to logout button

On logout

1. Click logout button
2. Delete key on server, if possible
3. Delete key locally
4. Button changes to login button

added Frontend label

changed milestone to %Agenda

added Priority: High label

changed the description

changed title from Add login logic to frontend to Add login to frontend

mentioned in issue #16 (closed)

closed