Clear cache on a container should clear the sources

Expected behavior

When we clear the cache of a container with resource.clearCache(), if resource is a federation of multiple sources, the command should remove all the sources from the cache.

What's happening?

Today, if we clear the cache of a container, it keeps the children in the cache, and remove only the container. ie:

/*
container
   user-1
   user-2
   user-3
*/

container.remove(user-1)
container.clearCache()

/*
container -> reloaded
    user-1 -> not reloaded
    user-2 -> not reloaded
*/

if user-1 and user-2 are containers, we should also clear them, because they might have changed.

This would fix applications/sib-app#505