[FEATURE] - Descriptive exceptions.

[Johannestegner]

The current implementations (might be exceptions! :) ) have quite generic error messages. We should go through the cases where we throw errors and create a list of actual error messages which could be used over the different solutions.

I'm alright with it differing slightly over the various packages, but the more "standard" the better.

Example:
Error thrown on parse returns (in some packages at the least) "Invalid personnummer".

This doesn't say much.

If it threw a PersonnummerException with the message "Month out of range", it would be a lot easier to see what went wrong.