[package] Rewrite the packaging subsystem.

We now support multiple packaging formats, and installation is not
(necessarily) tied to target. Using PACKAGE_FORMAT, a developer can
select between packaging formats offered by Theos and any installed
modules.

When building debs, we no longer use package_version.sh three times: we
cache the name of the last-built package, and we only bump the version
number once. We recover the bumped version from _/DEBIAN/control before
the package is built.

Targets now define their preferred default package formats, and whether
they're remote or local. _common/install_deb_* have been removed, as
they have become useless.

This merges in 5d135e5 ("!WIP [makefiles] Copy the deb to a temporary
location and install it during the same SSH session.") from
dhowett/dev/experimental-rebased.

From: Dustin L. Howett <dustin@howett.net>

git-svn-id: http://svn.howett.net/svn/theos/trunk@613 4410221e-0ddf-4ce3-99c0-2db6c0dbc727