Save passwords and user names

Allow for saving of user name and password for servers.
When logging in, a checkbox with the label "save password" should be available. If clicked, the entered info should be saved to a file.
Note that we'll save the password, so we'll have to make sure that the file has the correct access settings. To provide better security, we should preferably hash the password (since a user often reuse the same password over and over on different sites, so if an attacker gets the password to one account he/she can often reuse that on other), but since cyphesis have no support for logging in with hashed passwords we'll skip that for now.