P.V. SUPA GoodStuff integration

P.V. SUPA GoodStuff integration

This impliments a "Server Add-ons" module for integrating P.V. Supa's RFID
product known as GoodStuff with the Evergreen staff client.

To activate it, you should add the identifier "pv_supa_goodstuff" (without the
quotes) to the list managed by the Admin->Workstation Administration->Server
Add-ons menu action within the staff client.  You will need the
ADMIN_SERVER_ADDON_FOR_WORKSTATION permission to do this.

After doing this and clicking the Update Active Add-Ons button, the interface
will refresh and show a GoodStuff tab in the Add-on Preferences section.  Within
this tab you will have the option of specifying the hostname and port for the
GoodStuff hardware. There is also an "Enabled" setting that needs to be checked.

Currently three interfaces have been integrated:
* Circulation -> Check In Items
* Circulation -> Check Out Items (where you scan the patron barcode)
* Circulation -> Check Out Items (where you scan the item barcodes)

Each interface gets an RFID checkbox if the "Enabled" preference has been set,
that can activate/deactivate the functionality on a per interface basis.  The
checkbox states persist (i.e. are sticky).

Signed-off-by: Jason Etheridge <jason@esilibrary.com>