[wallhaven] rewrite

- use API
- remove login support, add 'api-key' option
- remove support for "alpha" subdomain - alpha.wallhaven.cc used numeric
  IDs that can't be translated to the new ID system
- support direct links to wallpapers

docs/configuration.rst

@@ -884,6 +884,18 @@ Description Use `youtube-dl`_ to download from video tweets.
 =========== =====
 
 
+extractor.wallhaven.api-key
+---------------------------
+=========== =====
+Type        ``string``
+Default     ``null``
+Description Your  `API Key <https://wallhaven.cc/settings/account>`__ to use
+            your account's browsing settings and default filters when searching.
+
+            See https://wallhaven.cc/help/api for more information.
+=========== =====
+
+
 extractor.[booru].tags
 ----------------------
 =========== =====

docs/gallery-dl.conf

@@ -134,6 +134,10 @@
             "retweets": true,
             "videos": false
         },
+        "wallhaven":
+        {
+            "api-key": null
+        },
         "booru":
         {
             "tags": false

docs/supportedsites.rst

@@ -99,7 +99,7 @@ The /b/ Archive      https://thebarchive.com/            Threads
 Tsumino              https://www.tsumino.com/            Galleries, Search Results                          Optional
 Tumblr               https://www.tumblr.com/             Images from Users, Likes, Posts, Tag-Searches      Optional (OAuth)
 Twitter              https://twitter.com/                Media Timelines, Timelines, Tweets                 Optional
-Wallhaven            https://alpha.wallhaven.cc/         individual Images, Search Results                  Optional
+Wallhaven            https://wallhaven.cc/               individual Images, Search Results
 Warosu               https://warosu.org/                 Threads
 Weibo                https://www.weibo.com/              Images from Users, Images from Statuses
 WikiArt.org          https://www.wikiart.org/            Artists, Artworks