BUG-994: reorganize SchemaPath into a tree

Instead of storing the entire path in the scemapath object, this patch
reworks the class such that it holds 0ne component of the path and a
reference to the parent path.

Change-Id: Ic029c84db9817f9799070c5c4aad7fc3f5fa13b1
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-994: reorganize SchemaPath into a tree"