Code improvements and clean-up

[buep]

These observations were made during a little workshop we had around testing in PAC.

We should improve in these areas when we do changes in the near future:

• class name doesn't match test unit file name
• unit test collection,but more or less they are functional tests and should be either made real unit tests (only import can be the class under test) or moved to the functional test suite
• docopt parser isn't yet tested properly, but some examples are made
• PAC have several error reporting strategies, but they are not clear and must be explained. E.g. our strategy could be:
  • without verbose PAC only reports errors, no stack traces if failing
  • with one verbosity level PAC report error and stack traces if failing
  • with two verbose PAC reports in addition data object in important places during code execution