JSDebugger: Enable break on events.

The user can request Javascript break on event. The user can provide
this info in the Breakpoints Window and provide the slot which will
be called when the event occurs. For example: specify "onTriggered" if
you need to break on Timer triggered event.

Change-Id: If936d7402f5978a182132fdcca75515588364e16
Reviewed-on: http://codereview.qt-project.org/4758


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>