Added support for default value of "Select Pick Up Location" when placin...

...g a hold or a storage retrieval request, and driver support for that in VoyagerRestful.

Our usability studies indicate that user's often forget to check the pick up location when placing holds. This makes it possible to force the user to choose while maintaining the possibility of having a default (e.g. when there isn't really anything to choose from). The slightly weird handling of the setting (0 => false) is because PHP doesn't handle false as a boolean in an ini file.