rhbz1148242 - Clear document/locale stats after a copy

Pull Request: https://github.com/zanata/zanata-server/pull/598

Squashed commit of the following:

commit 3e054b4a903b7967da33a074c0a645b6f7ef699a
Author: Carlos A. Munoz <camunoz@redhat.com>
Date:   Thu Oct 2 09:07:37 2014 +1000

    rhbz1148242 - Clear document/locale stats after a copy trans.

    When the stats are reloaded, up-to-date stats will be re-calculated.