Try harder to make sense of user input in the login dialog

[KitsuneRal]

For now Quaternion treats 'Connect to server' as a base URL for a homeserver to, well, connect to. In case there's no workable homeserver found at 'Connect to server' base URL, Quaternion could additionally try some non-specced heuristics. This issue in particular suggests to try the 'Connect to server' URL as a serverpart and apply .well-known discovery procedure to it. Given that an attempt to connect to a homeserver may take noticeable time to prove unsuccessful (currently it's about a minute if the server returns errors quickly, and more than 3 minutes if all requests time out) it may make sense to ask the user whether they want to apply such heuristic or rather figure out themself what was wrong with their input.