RFC Importing Implementation

Original discussion: #2769

Based on OpenGraph syntax.

RFC web importing was a legacy feature which allowed HDT to turn a URL into a deck. It has since been replaced with deckstrings, small base64 snippets which contain all the deck metadata needed and which are natively supported in Hearthstone, HDT, and all other deck trackers.

Please see the deckstrings documentation for information on how to create and parse deckstrings.