Don't use keg-only and pouring jargon.

This is unnecessarily confusing to end-users and the "fun" naming doesn't really communicate anything. @mistydemeo and I talked about this.

CC @adamv @mistydemeo @jacknagel @tdsmith @asparagui for thoughts and review.
Agree with Adam and @DomT4 that while this is descriptive it feels really clunky.

How about "private"? E.g. rather than talking about "linked" vs "unlinked", make the distinction of packages that are globally available and ones that are kept private.