Add options to customize selector logic

[shiraeeshi]

Here are some new options to support a use case mentioned in this question: --with-inherited - allows to run inherited methods as tests --with-undefined - allows to run methods that was not defined in the class, but was added later --with-tools-decorators - lets istest, nottest decorators contribute to selector logic --with-tools-decorators-only - runs only those functions and methods that was decorated with istest (a class containing a method should also be decorated)