Add facilities to filter out anonymous classes and anonymous functions when analyzing BC breaks

[Ocramius]

[asgrim]

As mentioned in the PR, anon functions is not within the scope of this project, so ignored in fix in PR #60

Note: the issue specifies filtering out anonymous functions too, but we don't actually reflect on functions at all at the moment; it is all just ClassBased, InterfaceBased and TraitBased roots; plus the top level is the CompareClasses implementation...