Access errors_mod directly

[Mikolaj-A-Kowalski]

Following the #35 the fatalError subroutine has been moved to a separate module errors_mod, which is intended to handle all the error and warning messages.

However to avoid too many git conflicts the fatalError is currently imported into genericProcedures and all other files get it via genericProcedures module like before.
We should import the fatalError for errors_mod directly though. I think when the most outstanding PRs are merged we can do it in a single PR for all files.