Add option to not consider word boundaries when processing keyword filtering (#7975)

* Add option to not consider word boundaries when filtering phrases

* Add a few tests for keyword/phrase filtering

db/migrate/20180707154237_add_whole_word_to_custom_filter.rb

@@ -0,0 +1,17 @@
+require Rails.root.join('lib', 'mastodon', 'migration_helpers')
+
+class AddWholeWordToCustomFilter < ActiveRecord::Migration[5.2]
+  include Mastodon::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def change
+    safety_assured do
+      add_column_with_default :custom_filters, :whole_word, :boolean, default: true, allow_null: false
+    end
+  end
+
+  def down
+    remove_column :custom_filters, :whole_word
+  end
+end