Updates and clarifications to broctl docs
Document which broctl options override Bro script vars
Update broctl.rst with "make doc" (no other changes)
Merge remote-tracking branch 'origin/topic/dnthayer/doc-changes-for-2.2'

* origin/topic/dnthayer/doc-changes-for-2.2:
  Update broctl.rst with "make doc" (no other changes)
  Document which broctl options override Bro script vars
  Updates and clarifications to broctl docs