Merge remote-tracking branch 'owncloud/master' into db-convert-tool

* owncloud/master: (137 commits)
  add comment to clearify when a skip in the foreach happens
  remove obsolete code
  Always define sendmail_is_available
  [tx-robot] updated from transifex
  Make hardcoded exception messages translatable
  Disable sharing in trashbin app
  class Test_Config is already declared
  [tx-robot] updated from transifex
  using array_key_exists() instead of isset() - required because in case the value is null isset is returning false
  fixing undefined exception classes
  unit test testSetAppValueIfSetToNull() added
  unit tests for dynamic backend registration
  ignore underscore.js in scrutinizer.yml
  adding ownCloud globals to jshintrc: OC, t, n
  Use git checkout on directory as some files may not be in git resulting in, e.g.:
  adding underscore.js
  reduce code duplication, fix parse error, prevent page reload on hitting enter while changing the display name - refs #8085
  translations for oc-dialogs reside in code
  Fix copy conflict dialog translation
  [tx-robot] updated from transifex
  ...