elm: Add support for Efl.Model in Elm.Fileselector

elm: Add support for Efl.Model in Elm.Fileselector

Elm.Interface.Fileselector now supports Efl.Model objects, allowing users
to work with paths from different data models.

Example of model attribution:

ELm_Fileselector *fs = eo_add(EFL_FILESELECTOR_CLASS, NULL);
Efl_Model *model = ...;
elm_interface_fileselector_model_set(fs, model, NULL);