Trac login, deliberate annonymous/authenticated login

Remove all URL printing from the login method, passwords are still revealed in the error messages from the XMLRPC library. This will also simplify the method.
* Remove all code that removes passwords from URLs
* Remove printing of URLs and XMLRPC errors (keep it but commented out).
* Use same wording like Launchpad login:
    * Look up good wording.

Mostly resolved:

The Trac controller does currently fall back to anonymous login when the password fails. It is also impossible to deliberately login anonymously, you enter a bogus password to login anonymously.

* Wrong passwords are not reported when the program logs into Trac, instead it fails later.

* Anonymous login takes a long time because the program tries to log in authenticated first.

* The login method writes a lot of unnecessary output, and it is also complicated because it needs to remove the password from the login URL.

Therefore implement a way to login anonymously, and fail in the login method when the password is wrong.