Improve VirtualRealPorn network scraper (replace xpath scraper with fully functional Python scraper)

[nrg101]

This builds upon the Python base class work in #1288

It provides:

• sceneByName and sceneByQueryFragment, for scene search by string (e.g. title or partial title)
• sceneByFragment, for scene search by existing fields (Scrape With...)
• sceneByURL, for scene scrape by URL field
• performerByName and performerByFragment, for performer search by string (e.g. name or partial name) (Scrape With...)
• performerByURL, for performer scrape by URL field

for the six network sites of VirtualRealPorn

I've run the scraper successfully on 160 scenes, mostly virtualrealtrans.com, but some virtualrealporn.com and virtualrealpassion.com.