Additional stash match rules

[toshski]

The main change adds extra rules for matching to Stashdb.

Currently, to match scenes to Stashdb, the URLs are used to match (optionally with regex expressions to extract the matching values). For some sites this does not work well, particularly when using an aggregator site like SLR or VRPorn, to a main site, Wetvr. The scene URL for eg Wetvr. The scene URLS in Stashdb are unlikely to match the URL scraped from SLR, etc.

This change allows the user to specify additional rules to match scenes to Stashdb.

• studio_code, matches the Stashdb Studio Code if available, to the XBVR scene_id (minus the xbvr scene_id prefix)
• title/date
• title

Multiple rules can be specified, and they will be evaluated in the sequence, they appear. e.g. you can specify "title/date" and just "title", but you should specify "title/date" date first as it is more specific.

These rules are not as strict as the URL matching and could lead to false matches. The balance between wanting correct matches vs more unmatched scenes is a matter of preference, so this change is for the users to decide for themselves whether to use them. Existing matching remains unchanged.

Additional change:
You can also specify matching rules of an XBVR site to multiple Stashdb sites. This is maybe useful where scenes are moved between studios, or if an aggregator has one site but is actually multiple sites in Stashdb. e.g. you could setup a custom scraper to Thundercock on VRPorn, this is NuaghtyAmerica site which in the past use to be Big Cock Billy, so when search Stashdb, you could search both Thundercock or Big Cock Billy.

Example json mapping Thundercock to 2 stash studios using the title (note: the name tags are for commentary and not required)

 "thundercock-vrporn": [
  {
	"Name": "Thundercock",
    "StashId": "f405f909-d3db-4df3-9f99-0500d769f527",
    "Rules": [
      {
        "StashRule": "title"
      }
    ]
  },
  {
	"Name": "Big Cock Bully",
    "StashId": "d2451a9f-6bbc-408a-a309-5d9572a3cb08",
    "Rules": [
      {
        "StashRule": "title"
      }
    ]
  }
]

I'll try and find time to set up a wiki article.

Also requires #1889 to fix bug with rules not been loaded