Use functools.wraps in decorators

This makes sure docstring and name are inherited from the decorated
definition. Fixes decorated unit tests, which previously where skipped
since their name did not start with test_ after decorating.


git-svn-id: https://humgenprojects.lumc.nl/svn/mutalyzer/trunk@619 eb6bd6ab-9ccd-42b9-aceb-e2899b4a52f1