Issue253 testexamplescoverage

[mwetter]

This closes #253.

Todo: @MichaMans, can you please address the following:

• Replace print with a call to self._reporter.writeOutput. See for example regressiontest.py, line 2634. This way, the message will also be in the log file.
• I would prefer to call the new method printCoverage rather than get_models_coverage because it only prints something, it does not get anything. Also, we typically use camel case for function names (although not consistently).
• Add doctest (and ideally a unit test).

A cleaner implementation would probably be to have a method _getCoverage that returns the coverage and everything you need to print, and a wrapper method printCoverage that calls _getCoverage and prints the coverage. Then, you can also write a unit test for _getCoverage to make sure it won't break when people work on BuildingsPy, and you can put the coverage in other (web) documentation that you want to serve from your CI environment. At the minimum, you should add some doctest in its documentation so it is clear how to use it and it will be tested with make doctest