Improve observation of files

A file in JCR is represented by at least two nodes, the nt:file node and a child node named jcr:content holding the contents of the file (and metadata).
This has the consequence that if the contents of a file changes, a change event of the jcr:content node is reported - but not of the nt:file node.
This makes creating listeners listening for changes in files complicated, as you can't use the file name to filter - especially with glob patterns (see JCR-4044) this becomes troublesome.
In addition, whenever you get a change for a jcr:content node, you have to check if the parent is a nt:file node and decide based on the result.
It would be great to have a flag on the JackrabbitEventFilter to enable smarter reporting just for nt:files: if a property on jcr:content is changed, a change to the nt:file node is reported.
See also SLING-6163 and OAK-4940