Configure on the location if the contained products must be part of a package
and if you allow multiple package.  When the module is installed, by default
there is no restriction on the locations.

The options are:

  * Mandatory and unique: The location cannot have products not part of a
    package and you cannot have more than 1 package on the location
  * Mandatory and not unique:  The location cannot have products not part of a
    package and you may have store multiple packages on the location
  * Not mandatory: The location can contain products not part of a package
