Allow to search in all sheets.
Find all now creates new dialog describing all matching cells.

Change-Id: I36a9bee314b620384937fff074680022397c8c5f
Reviewed-on: https://gerrit.libreoffice.org/5886Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>