The UI for placing a frame in the background is confusing because:
-in menus, the icon looks like a checkbox, but functions as a radio button
-it isn't obvious that "in background" is the opposite of "wrap through"
-it doesn't act like the checkboxes below it like "First paragraph"
-in dialog boxes, it is actually implemented as a checkbox toggle.

So it looks like a checkbox, and you can enable the checkbox, but
once enabled it can never be disabled.  (The currently designed way is to
select wrap off/page/optimal/through in order to disable in background.)

This patch creates FN_FRAME_WRAPTHRU_TOGGLE to replace
most uses of the previous function.

Change-Id: Ia46ddbd47899e8ca569bf3adb2b1c4ad7cfa1920
Reviewed-on: https://gerrit.libreoffice.org/39673Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Heiko Tietze <tietze.heiko@googlemail.com>