Fix messages in cbq shell

In cbq shell, the words "No Input Credentials" should be "No input credentials".

Isha, can you sit with Prasad and do a top to bottom review of all messages and errors in cbq shell for grammar, spelling, capitalization, etc.

Also, all user-facing messages should be in a separate messages.go file, just like we do for errors. They should be defined as global constants that are used in the code.

Thanks.