Adjust parts of the WBE to reflect a little better what
the components do and explain better arrows mean and turn it
into an svg to scale and present better (and just in generally look
better on all svg supporting browsers; which is all browsers
now-a-days).
* Changes the diagram to add 'executor' to engine block.
* Adjusts communication for engine -> proxy -> workers is
composed of task requests to revert/execute.
* Adjusts communication for worker -> proxy -> engine is
more of capabilities, notifications and results (from
prior execute/revert) requests.
* Adds endpoints into worker box.
* Changes to using 'executor' + threads in worker; the thing
that the worker uses to actually execute work (this is
different than the executor in the engine box, although they
are somewhat related in what they do...).
Change-Id: I068bdd4f912ac05f2416eb03fc07cd68656b9a43
2cd90745ea