Figure out a better solution to fromString.

[gburtini]

The XPathQuery and XPathNode objects both support a partially implemented fromString at the moment. It is left out of the documentation because it is not well supported. They rely partially on the Jison XPath parser and partially on a custom parsing implementation.

There's two options here: eliminate support and only have the already built fromDom (most reliable) or greatly evolve the support to work from the Jison parse tree. Note that Potent requires the fromString support to provide a nice UX.