Test runner with annotation filtering

I propose a test runner with filtering based on annotation. 

It is a simple `BlockJUnit4ClassRunner` providing two additional annotations, `@Include` and `@Exclude`, which can be used to specify include/exclude clauses agains annotated test methods. 

Methods without annotations are treated gracefully if no include clauses are specified. I tried to stick to the include/exclude logic already implemented for the `Categories` runner. In the future, these two runners could be merged, as they work in a similar way.

**One little problem:** I tried to find a smart way for skipping framework annotations while filtering, but at the end I preferred to create a protected `getIgnoredAnnotations()` method that simply returns a `Set` of... well, ignored annotations.