Add phing script for upgrading modules from .make file. #116

Create phing/upgrade-contrib.xml to run drush make on existing Drupal instance which will invoke drush/drupal-org-contrib.make.
It should work as standalone and when called from build.xml (similarly like generate-ads.xml).
Then create ads-upgrade phing command to invoke that script and add make upgrade into Makefile to run that update.