Several Parsoid-specific tests for serializer/parser edge cases.

Added several serializer tests
* For catching future serializer regressions.
* For fixing existing incorrect serialization.

Added couple parser tests
* For testing encap of partially-tpl-generated attribute key
* For testing lists interrupted by comment-lines

Change-Id: Ifbb7da59f65e790b66a621b7964179e4eb1f3fc4
Merge "Several Parsoid-specific tests for serializer/parser edge cases."