Improve support for MediaWiki wikis with non-standard URLs

[stjohann]

Since the addition of support for different servers, it uses /wiki/$1 pattern to detect whether something is a wiki or not. Judging by interwiki map on Meta-Wiki, we can see that this is not enough to determine whether something is a MediaWiki wiki or not: they can also use simple /$1 or something convoluted like /index.php?title=$1 or /index.php/$1 and still be valid wikis.

This poses two problems for the current code:

1. Easier one: support more wiki URL patterns in linking bot. This can be done by including checks for more URL patterns and fetching APIs of those wikis for their interwiki chains. I should come up with a good way to know (and even remember) wiki URLs somewhere, because it might be silly to ask, say, Google for /api.php a hundred times.
2. Harder one: update the current code to use /api.php at the end of the string as a way to validate wiki URLs rather than /wiki/$1. That way, the bot will ask the API and get and remember the article path from there. I didn’t hear any requests before asking about this problem, but it will be a good thing to do. All the old values with /wiki/$1 will need to be deprecated and updated in the configs.

The removal of deprecation of old URLs will introduce a new major version (v.N.0.0) of the bot.