Provides a cache for reflections, so that classloader scanning over the same classloader for the same package
multiple times doesn't need to be done.
This is most useful in tests, when each test starts a new FakeApplication, and so things like Ebean scan the
classloader for @Entity annotated classes in a given package. Profiling shows that without this cache, over 90%
of a tests time might be spent in classpath scanning.