CMFActivity: Allow defining node identifier in zope configuration file.

Allows giving more compact and user-meaningful names if desired.
If used, makes in-ZODB data (processing/validation roles) independent
from process' network binding, removing the need to re-configure
CMFActivity after changing network.
Also, update AlarmTool usage of getCurrentNode (and related).
Also, replace AlarmTool's manageAlarmNode input field with a select for
convenience.