#375 Add checkbox for sharing when adding a printer

[lazyDesertMan]

In the printer add menu there is no checkbox or any other way to specify whether to use shared access or not when adding a device. The device is set to the default value defined in CUPS after adding.

The patch adds a new line to the "Describe Printer" section, containing a checkbox that allows users to specify whether to use shared access or not for the device being added