The page handling implementation is a little bit tricky, because
the elemnt list is not handled like a grid but a list. Normally
one would keep the horizontal cell and just scroll vertically.
Instead this implements a kind of circle.

Vertical offset is consistet, so you have the same amount of
steps for up and down, but up runs left and down runs right.

Change-Id: I296a46e98f7e00a59fd0a0ba358c981b49ac86cd
Reviewed-on: https://gerrit.libreoffice.org/72793
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>