ParserTests: Fixed selser change generation and application

* Cleaned up selser change generation code in parser tests.
  - Generates change types based on whether a dom subtree is
    editable or not, whether a node can be edited or not,
    and the node type.

* Apply change trees as specified.
  - Supported change types: Attr Modification, Add, Delete, Change
  - Add, Delete, and Change types now modify a DOM subtree as
    necessary

* 2000+ additional tests generated in selser.changes.json

* Regenerated parserTests blacklist file.

Change-Id: I925833f24c3b1c0d62958ebd621085ac34c5a1d8