SLING-3072 -  Repository: API needs a single method to create a node and
set its non-binary properties

The Repository interface now has a single newAddOrUpdateNodeCommand . As
a side effect, extra properties for nt:file nodes serialized in a
${NODENAME}.dir/.content.xml file are now propertly saved.

git-svn-id: https://svn.apache.org/repos/asf/sling/branches/tooling-ide-vlt@1524999 13f79535-47bb-0310-9956-ffa450edef68