Issue #305 - Implement duplicated QAS removal

* Adds a way to remove the duplicated QAS entities `questionID -
  surveyInstanceId` using the testharness
* It uses the configured backend for processing
Updated 1.6.0 notes to include number of languages and which are experimental.
Issue #305 - Reimplement duplicated QAS deletion

* Use Memcache service instead of local map
* Spawn a new call if we need to process more entities
Merge branch 'master' of https://github.com/akvo/akvo-flow into feature/dashboard_test
Merge branch 'develop' of https://github.com/akvo/akvo-flow into feature/dashboard_test
Dropdown Survey Group Selection Refactor with jquery trigger(change) event.