Merge pull request #4300 from adobe/nj/ResearchLiveHTML

[ResearchLiveHTML] Initial implementation of incremental update
Incremental tests are turned off, a couple of tests are failing.
Checkpointing the work, because the differ is close to handling
element inserts/deletes and text insert/delete/replace. Still needs
to handle moves.
remove bogus subtree match error
Store nodeMap on subtrees so incremental diff works again (a couple unit tests are still failing but they're actually in the full diff)
Correctly calculate node ID for text nodes
Add _dumpDOM utility method
Make text replacements work in live UI again
Added (terrible) code to push element and text insertions/deletions to the browser
Update marked ranges for changed subtree. Delete deleted nodes from node map.
Comment out some logs
Don't update if we think we're in an invalid state. Detect more cases of invalid HTML in parsing. (Still doesn't detect unbalanced <> in some cases.)