Allow user to supply full prefix or just domain

[scottf]

Overview

1. Accept full prefix, turning $JS.API. into <prefix>.API.
2. Accept domain, turning $JS.API. into $JS.<domain>.API.

Clients and Tools

• [x] Go @wallyqs
• [x] Java @scottf
• [x] JavaScript @aricart
• [x] .Net @ColinSullivan1 @scottf
• [x] C @kozlovic
• [x] Python @wallyqs
• [x] Rust @Jarema

Other Tasks

• [x] Update client features spreadsheet

Client authors please update with your progress. If you open issues in your own repositories as a result of this request, please link them to this one by pasting the issue URL in a comment or main issue description.

[bruth]

Appears to be completed, closing.