Update to Model to reflect LicensingBasis

LicenseType property removed from data model and replaced with
LicensingBasis, which better reflects the sense of how an administrator
of a store catalog will currently set licensing information in the
application. References to LicenseType/LicenseTypes have been removed
and replaced with LicensingBasis/LicensingBases
Update to Edit options for Catalog Entries

Added facility to edit LicensingBasis via a dropdownlist in
~/Catalog/Edit. The DropDownList takes the value of the LicensingBasis
from the record for that catalog entry.