CORE-4600 Refactor DiskResourcePresenterImpl refresh methods.

Refactored the DiskResourcePresenterImpl#doRefresh so that it only fires a DiskResourceRefreshEvent.
Refactored the DiskResourcesEventHandler to implement DiskResourceRefreshEventHandler, which will now call DiskResourcePresenterImpl#refreshFolder.
Refactored all other classes to call only the DiskResourcePresenterImpl#doRefresh method.
Refactored the DiskResourceRefreshEvent into the ui-commons-module for use by the caching service facade, and to remove the obsolete 'tag' parameter.
Fix for DiskResourceViewImpl#removeChildren.

A Kludge was needed in DiskResourceViewImpl#removeChildren to remove the given parent folder from the TreeStore, then re-add it without children.
This is needed because the TreeStore doesn't remove children from their parent's TreeModel wrapper in the TreeStore#removeChildren method.
So re-adding a child removed by removeChildren will add duplicates to its parent's TreeStore model.