man page nits

[gdt]

23.8.0:

• autoremove uses "orphan" but does not define it. I suggest to say "removes packages which are auto-removable and which are not a dependency of a non-autoremovable package. In other words, any package which is auto-removable is removed, if it is no longer necessary."
• keep uses auto-removable (yay!) but then also says "keep-able".

Also the issue in #101 where the semantics of install when the system is not in an upgraded state are unclear.

[jperkin]

Yeh I don't much like any of the current nomenclature around this, I'll try and come up with something a lot more orthogonal in the next release.

[gdt]

I think auto-removable is fine, and I was very pleasantly surprised to see it; I had not myself come up with a better word. This is the vestige of "keepable" which I bet made sense in French before it was translated to English and while it nerd-makes-sense I think most would find keepable confusing. autoremovable is wordy but easy to understand. So I think we don't need a naming rototill as much as cleaning up an 80% change in terminology to 100%.