Add merge() methods to IndexValueStore and InternalList, which merge
another store/list in to the current one and return a mapping
translating old indexes to new ones.
Also add functions that, given such a mapping, traverse a linear
model data array and remap store/list indexes using simple logic for
annotations and node type-specific functions for node attributes.
Change-Id: I1e90755ced1a87c190947c037cf151c4d17cf8b7
converter.documentData contains the full data with metadata interleaved,
but it was being sliced using offsets relevant to the element data.
Change-Id: Iddbef23212da818a2a399b4abdc223aad130eb4e
See: I6daff5c5969e5fdc871f8f346cf790b4302ae080