ensures that the user context cache is cleared when users are saved which will work in LB environments.
Changes more HttpRuntime.Cache dependencies to ApplicationContext.Current.ApplicationCache.
cleared when media was deleted. Created base classes for cache refreshers, we now have a new event - CacheUpdated
which can now be used by code to execute on each individual server when any cache refresher is updated. Listening to events
normally only fire on the individual server so if people are wanting to refresh their own cache there was previously no way
to do that.
