Some more DOMDiff tweaks (continuation of 4170e8a9) + fixes to WTS

* When trailing children of a node were deleted mw:DiffMarker was
  not being added in DOMDiff. This makes a difference to the upcoming
  separator patch.

* Fixed WTS to more consistently skip over mw:DiffMarker during
  serialization. Important for correctness.

* 2 selser tests failing, 2 selser tests passing.
  - At least one of the failing selser tests is a result of WTS
    doing the wrong thing (which the upcoming separator patch will fix).

Change-Id: I60e6d1366b0d3894c995070a489adf8885425fae
Cleanup: Removed support for old-style templated attributes.

* We've been generating data-mw style templated attrs. for a while
  and production cache has also been cleared a few times since then.
  So, no need to carry around code cruft anymore.

Change-Id: I4e0dbcce2064857dd96de8d90bf90beea817e25f
Dont suppress newlines around <*include*> in html2wt mode

* 1 wt2wt test, 7 selser tests now green

Change-Id: I05d19575f5e37343209304d13dad70f70e0a5c2a