Bloody workaround hack for the fact that Chart does not handle
category/x-axis times internally and is not able to pass its own axis
numberformat to its own databrowser editor.

Change-Id: I016695ad0104366c0bb636b449a2014ade31aca3
(cherry picked from commit 711b34d5)
Reviewed-on: https://gerrit.libreoffice.org/17627Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>