New feature: Prompt for user + password

This is for users who don't like HeidiSQL to store usernames and passwords somewhere:

Activating this new checkbox will ask you for username and password on demand, each time you connect to this session. Both previously stored username and password are taken as the default credentials when prompting.

The only thing stopping me from using HeidiSQL now and recommending it to developers at my office is the fact that you can't do "prompt" for SSH tunnel username and password. We don't want to save those credentials, so that feature would be nice. :)