Display more informative and actionable error messages

These error messages were a bit short and contained technical jargon.
They did not give the user a good sense of how to proceed.

With this commit, the error messages are changed to clearly include
the important elements of a good error message:
1. What went wrong
2. Why it happened
3. How they can fix it themselves
4. How they can report the issue to get it permanently fixed for
   everyone

To do this, the setError() function is extended to also be able to
accept an optional explanation arguments, which is used to present
better information to the user.