Testing improvements after moving to gitlab

Now that we have moved to GitLab, the previous CI system is down, and we may need to run more tests manually for a while. All unit tests should now run under Ubuntu 20.04 with only the command "Catch [unit]" without having to use any of the exclude tags.

More improvements may be necessary:

• Some tests change files under version control. Store these in a temporary folder instead of changing the existing files to avoid adding unnecessary file changes