Add priority to sources for gurmukhi/translations

[Harjot1Singh]

Priority column + API override + example SQL query override

Should be simple, because right now, it's hard to select data when you don't mind the default sources, or just want to override the priority of 1 or 2.

Maybe do it z-index style, where the default list priority is assigned in 10s, so 100, 90, 80, 70, 60, 50 etc where higher number is higher priority.

Required before we release v5

[bhajneet]

Add field to indicate whether source is (in)complete