Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Improve the INDEX format. Whitespace improvements, format improvements, typo
and grammatical fixes.

Commit first portion of package module -- this includes the ability to view
categories, view packages, mark packages for installation, de-installation,
or re-installation, calculate and track dependencies, as well as ability to
review selections.

Still to come is the actual processing of selections (performing the
various actions associated with the user's selections, such as installing
dependencies first, then selections, etc.).