Use JaxbUtils instead of EventConfDao when saving eventconf.xml

Using EventConfDao for saving will replace everything inside
/opt/opennms/etc/events/ which is not necessary and makes the
troubleshooting process a little bit complicated.
Merge branch '1.12' of github.com:OpenNMS/opennms into 1.12
Merge remote-tracking branch 'origin/1.12'

Conflicts:
	features/vaadin-snmp-events-and-metrics/src/main/java/org/opennms/features/vaadin/events/EventPanel.java