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/test_helpers/iqdb_test_helper.rb

@@ -1,28 +1,6 @@
 module IqdbTestHelper
-  def mock_iqdb_service!
-    mock_sqs_service = Class.new do
-      def initialize
-        @commands = []
-      end
-
-      def commands
-        @commands
-      end
-
-      def send_message(msg)
-        @commands << msg.split(/\n/).first
-      end
-    end
-
-    service = mock_sqs_service.new
-    Post.stubs(:iqdb_sqs_service).returns(service)
-    Post.stubs(:iqdb_enabled?).returns(true)
-
-    Danbooru.config.stubs(:iqdbs_server).returns("http://localhost:3004")
-  end
-
   def mock_iqdb_matches(matches)
-    Danbooru.config.stubs(:iqdbs_server).returns("http://localhost:3004")
+    Danbooru.config.stubs(:iqdb_url).returns("http://localhost:5588")
     response = HTTP::Response.new(status: 200, body: matches.to_json, headers: { "Content-Type": "application/json" }, version: "1.1")
     HTTP::Client.any_instance.stubs(:post).returns(response)
   end