Trying to deal with issue described http://forums.modx.com/thread/32541/modx-revo-event-output-issue-in-plugin#dis-post-437548 so now modEvent::output() can be used for setting the output, instead of "semi-private" modEvent::_output, which should generally be used only for internal interactions.
Preserve value types in modSystemEvent::output()

Merge remote-tracking branch 'origin/pr/392' into release-2.2

* origin/pr/392:
  Trying to deal with issue described http://forums.modx.com/thread/32541/modx-revo-event-output-issue-in-plugin#dis-post-437548 so now modEvent::output() can be used for setting the output, instead of "semi-private" modEvent::_output, which should generally be used only for internal interactions.