Feature Update: Make Inactive Drivers Unqueryable in Shifts/ShiftTemplates New/Edit/Duplicate

[n1qqq]

As a(n) dispatcher/admin, such that when i select from the Address.driver drop-down, i do not see inactive driver Driver 1.

[n1qqq]

Design Choice (same as of #296 (comment)):

new: never display inactive drivers.
edit: display inactive drivers only if the ride already contains them. User can even add new stops with those inactive drivers.