Revise cacheing @Cacheable

We need to revise how we use Cacheable.
The cache keys are generated by toString() of method signature + arguments therefore we need to refrain from using complex objects - only primitives should be arguments to Cacheable methods.
Additionally need to remove all annotations from methods whose arguments are collections ASAP.
Finally we need Cache.flush() triggers as well so that objects are up to date when they are modified in YUM.