Improved error messages

As part of our rapid update cycle we have changed several error messages to make them less ambiguous and more informative.

Case in point, the login error message now looks like this:

Instead of a "user not found" in the title, the actual cause of the error is displayed (not the result) to help identify what needs to be corrected at a glance.

Instead of repeating the same thing in the body of the error message, some probably causes and a helpful tip are now being shown.

This should basically address 99.9% of login issues right there in the error message.