alarms version 2: move database cleanup from webadmin to service

It no longer makes sense that the cleanup of
old alarms be done from inside the webadmin servlet. This
option should be part of the alarm server.

The configuration properties have been shifted over to alarm.properties,
and the query utilities have been relocated to dcache core.

Target: master
Require-book: yes
Require-notes: yes
Acked-by: Karsten