[JcrDiff] Support creating matcher trees on any level

Currently matcher trees in JcrDiff can only be created from a root node.
To support diff matching on subtrees, the initialization of the ItemInfo (wrapping and mapping the tree) needs to be made more lenient.

To prevent such subtree matches to be marked as a Operation.Type.MOVE in PatchFactory the 'root' of a matcher tree (which now can be on any level) must be excluded from (strong) move matching.