[translate/translate] 869e12: Added a minimal Quality checker.

[Rimas K. <rq...@ak...>]

  Branch: refs/heads/master
  Home:   https://github.com/translate/translate
  Commit: 869e12530cd01d2bce98ae9c81e2697a46735545
      https://github.com/translate/translate/commit/869e12530cd01d2bce98ae9c81e2697a46735545
  Author: Rimas Kudelis <rq...@ak...>
  Date:   2017-06-20 (Tue, 20 Jun 2017)

  Changed paths:
    M translate/filters/checks.py
    M translate/filters/test_checks.py

  Log Message:
  -----------
  Added a minimal Quality checker.

This checker only checks for untranslated, unchanged and blank translations.