Same node and property name support

The initial MK abstraction mandated that the nodes and properties share the same namespace (http://wiki.apache.org/jackrabbit/RepositoryMicroKernel#Data%20Model). This is a regression from Jackrabbit 2.x, which supports same name nodes and properties (SNNP).

OTOH, the NodeStores can easily support SNNP and with proper escaping, the MKs can also support it.

We should try to keep the support for SNNP in order to keep backward compatibility for existing content, and also keep the support for importing XML documents with same attribute and element names.