This helps de-clutter action button groups and eases visual scanning.

This patch also contains little layout tweaks where needed to separate
the Help button from its neighbors when the dialog is too small.

Change-Id: I56aafdaf2a5351bd7bcb4db693e520fd5c5166ce
Reviewed-on: https://gerrit.libreoffice.org/13427Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>