Added rendering option to the highstate outputter

- Added an option to the minion config file that allows to return
  information only for those states that changed or failed, skipping all
  successfull states (issue #12648)
Changed the name of state_diff and fixed a bug

- Changed the name of the minion config variable state_diff to
  state_output_diff to make it more clear

- Fixed a bug where the output from changed states was not being showed
Merge branch 'diff-outputter' into develop
Erased debugger lines
Added state_output_diff to the minion config file
Merge pull request #13785 from mirath/develop

Fix to issue #12648. Option to get diff between last two highstates calls