iqdb: update API client to use new version of IQDB.

Replace the old IQDB API client with a new client for the new forked
version of IQDB at https://github.com/danbooru/iqdb.

Changes:

* The /iqdb_queries endpoint now returns `hash` and `signature` fields.
  The `signature` is the full decoded Haar signature, while the `hash`
  is a encoded version of the signature.
* The /iqdb_queries endpoint no longer returns `width` and `height`
  fields in the response (these were always 128x128).
* We no longer need the IQDBs frontend server, now we talk to the IQDB
  instance directly.
* We no longer send add/remove image commands to IQDB through AWS SQS,
  now we send them to IQDB directly. They are sent in a delayed job so
  that if IQDB is down, uploading images is still possible, the add
  image commands will just get queued up.
* Fix a bug where regenerating an image's thumbnails didn't regenerate
  IQDB, because IQDB silently ignored add image commands when the image
  already existed in the database.

test/functional/post_regenerations_controller_test.rb

@@ -6,6 +6,7 @@ class PostRegenerationsControllerTest < ActionDispatch::IntegrationTest
       @mod = create(:moderator_user, name: "yukari", created_at: 1.month.ago)
       @upload = assert_successful_upload("test/files/test.jpg", user: @mod)
       @post = @upload.post
+      perform_enqueued_jobs # add post to iqdb
     end
 
     context "create action" do
@@ -23,9 +24,6 @@ class PostRegenerationsControllerTest < ActionDispatch::IntegrationTest
 
       context "for an IQDB regeneration" do
         should "regenerate IQDB" do
-          mock_iqdb_service!
-          Post.iqdb_sqs_service.expects(:send_message).with("update\n#{@post.id}\n#{@post.preview_file_url}")
-
           post_auth post_regenerations_path, @mod, params: { post_id: @post.id, category: "iqdb" }
           perform_enqueued_jobs
         end