Convert chart axis scale tab page to widget UI.

Obs:
-Several widget positioning methods turned useless and were deleted
-Corner case related to axis origin untested (couldn't find where it is used)

Change-Id: I6a563c89ddcfbff62494ce7726f3e7d6089e6b57
Reviewed-on: https://gerrit.libreoffice.org/6730
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>