The mobile version of the list used string formatting functions
defined in DiveObjectHelper and declared in mobilelistmodels.h.
Very confusing. Move them to a separate source file where - in
the long run - all the string-formatting functions, which
are scattered all over the place, can be collected.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
