Add a toString to ContainerExtractionResult

It was popping up in the logs a bit too often
Turn more configuration files in samples

Similar to other configuration files, this commit
renames event-viewer.yaml and hornetq-configuration.xml
into .sample files; the advantage being that this
makes a bit easier to install deployment-specific
RPMs, without needing to --replacefiles anything.
Make menu shortcuts more mac-friendly

Behaviour on linux/windows remains unchanged.

Conflicts:
	yamcs-core/src/main/java/org/yamcs/ui/eventviewer/EventViewer.java
Fix packetviewer crashes when switching versions

The interpretation of the UI prefs for 'RecentFiles'
is a Vector in old Yamcs versions, and an ArrayList
in new Yamcs versions. This causes class cast
exceptions when switching between versions.

Clients with this commit integrated, will from
now on store this pref under 'RecentlyOpened'.

From that point on, old clients will no longer
crash. It might be necessary to manually
remove the pref one more time though.