OAK-1133: Observation listener PLUS

Restore the listener interface that I removed in r1561710, renamed to
a handler for similarity with other callback interfaces like
org.xml.sax.ContentHandler and to avoid confusion with JCR's EventListener.
Also introduced a nodeReordered() method for more fine-grained handling
of reorderings.

Adjusted the EventFilter.includeReorder() method to also take a destName
argument so it can be included in the filtering decisions. For example
reorderings to before hidden or non-accessible nodes should probably not
be reported.

Include a FilteredHandler class that hides the event filtering mechanism
below the ChangeHandler interface.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1562102 13f79535-47bb-0310-9956-ffa450edef68