Fix #3430: Accept the search[id] param in all controllers.

* Allow every controller to take the `search[id]` param.

* Parse the `search[id]` param the same way that the `id:<N>` metatag is
  parsed. So `search[id]=1,2,3`, `search[id]=<42`, `search[id]=1..10`, for
  example, are all accepted.

test/unit/application_record.rb

@@ -0,0 +1,19 @@
+require 'test_helper'
+
+class ApplicationRecordTest < ActiveSupport::TestCase
+  setup do
+    @tags = FactoryGirl.create_list(:tag, 3, post_count: 1)
+  end
+
+  context "ApplicationRecord#search" do
+    should "support the id param" do
+      assert_equal([@tags.first], Tag.search(id: @tags.first.id))
+    end
+
+    should "support ranges in the id param" do
+      assert_equal(@tags.reverse, Tag.search(id: ">=1"))
+      assert_equal(@tags.reverse, Tag.search(id: "#{@tags[0].id}..#{@tags[2].id}"))
+      assert_equal(@tags.reverse, Tag.search(id: @tags.map(&:id).join(",")))
+    end
+  end
+end