Support multiple inheritance of @Categories

We are using JUnit Categories together with Surefire's <includes>/<excludes> tags in a Test hierarchy. However we have observed some inconsistencies in the resolution.

Example: 

• AbstractTest is tagged with @Category(CategoryB.class)
• TestA extends AbstractTest and is tagged with @Category(CategoryA.class)
• When running Surefire with <include>CategoryB</include>, TestA is not executed.

There are a few more failure cases, written as (integration/unit) tests. I have provided a PR with a fix.