Editor: New option for surrounding auto brackets

Notice that this option already existed in the auto completer. However,
from the user perspective it was synchronized with auto insert brackets.

Task-number: QTCREATORBUG-5835
Change-Id: Ia87a2ca38d89dba51380a4fdb58a5a3689ed9265
Reviewed-on: http://codereview.qt-project.org/4885


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: hjk <qthjk@ovi.com>