Introduce ActiveAlarmTable service

An ActiveAlarmTable holds the current system alarms (stateless and stateful). We'll re-use ListenerServiceMBeanSupport to subscribe to any system notifications to feed the alarm table with notifications that are considered to be stateless alarms.

Stateful alarms need either mbeans that can understand our stateful alarm notion, or special mapping through a 3rd mbean that we'll introduce further.

The table should be kept small (normally dozens of entries) and must allow the "acknowledge" of the alarms, i.e. the operator saw the alarm. Stateless alarms are removed from the table when acknowledged (since the system won't clear them). Stateful alarms must be cleared from the system, as well.

In a future version we could have a shared table between instances of a jboss cluster (with TreeCache) to show the collective alarm status of a cluster.

The table itself produces notifications whenever updated, so a manager could fetch the initial list and then subscribe for alarm table notification updates.