JCR Imports Need to Respect or Ignore Repostory-Level Semantics

The JCR import capability is subtly broken in that it has fallen out of compliance with section 7.3.3 of the 1.0.1 spec as we've added features. This section mandates that imports must either respect or skip features with repository-level semantics. For example, if a node with a mixin type of mix:lockable is imported with the jcr:isLocked property set, we either need to update the repository to treat that node as locked (which requires updating /jcr:system/mode:locks) or reset those properties to a valid default value.

In a larger sense, we need to test that importing the /jcr:system/jcr:nodeTypes branch will either import the node types correctly (and update RTNM) or will fail in some manner. Same for /jcr:system/mode:locks and /jcr:system/mode:namespaces.