Adds BinaryBeast::clear_expired_cache - so that like clear_cache, it can be used without having to worry about whether or not BBCache is configured
BBCache now allows passwords to be null
previously if password had been null, it would have flagged the cache as not being configured,
and therefore would not be used by the BinaryBeast class
Adds BBCacheTest PHPUnit test, for testing the local caching library
Adds assertServiceLoadedFromCache and assertServiceNotLoadedFromCache to bb_test_case
Adds @group for selective unit testing