Repurposing html() to be setter/getter and adding rawHtml() for plug-in ...

...development access. Deprecating xhtml() and _html()
Generally, for tests, we would want to use `rawHtml(html)`.

Using `html(html)` will, in some cases, probably introduce modifications to the HTML and we would end up starting the test with DOM that is different than what we had intended.

Therefore, `rawHtml(html)` it is, for most test.

"Most tests", because some tests may check the parser, itself. I would imagine that even in most (if not all) of those, `rawHtml(html)` would still be the desired setter function, because the parser is most likely tested on the way out, using `wymEqual` without the `skipParser` option.

Is this clear?