Introduced new ResourceType enum for AdminEvents which lists
the current supported ResourceTypes for which AdminEvents
can be fired.
Previously it was difficult for custom EventListeners to figure
out which ResourceType triggered an AdminEvent in order
to handle it appropriately, effectively forcing users to parse
the representation.
Having dedicated resource types as a marker on an AdminEvent helps
to ease custom EventListener code.
We now also allow filtering of admin events by ResourceType in the
admin-console.
Signed-off-by: Thomas Darimont <thomas.darimont@gmail.com>
