Update the mute implementation to the current codebase

Make it part of the info thing (and do a migration to ensure it's there)

priv/repo/migrations/20190219192317_create_user_mutes.exs

@@ -0,0 +1,7 @@
+defmodule Pleroma.Repo.Migrations.CreateUserMutes do
+  use Ecto.Migration
+
+  def change do
+    execute "UPDATE users SET info = jsonb_set(info, '{mutes}', '[]'::jsonb);"
+  end
+end