[Model] Add "static rows" in the model
[Model] Add "static rows" in the model

This allows inserting a static row into the model. It will be
inserted before the actual search/browse results. This is useful
for BrowseModel that wants to edd e.g. ".."-row for moving up a
directory

Signed-off-by: Jussi Kukkonen <589e25658b1bfd3646cd0c60eea9e9594b5e0b5b@intel.com>

rmerlino/dleyna-control,markdryan/dleyna-control,01org/dleyna-control,lferrandis/dleyna-control,jku/dleyna-control