Add ability to import deb packages while building the image

This adds a couple of scripts to bin, namely:
 - `deb2tcz.sh`: imported from TCL, modified to work with Bash and relative paths
 - `download-deb-pkg-list`: downloads and parses a Debian package list
 - `download-deb-pkg`: downloads deb packages from a Debian mirror

In addition, it modifies `build-bundle-file.sh` to differentiate between .deb and .tcz files, and install both appropriately.

Lastly, it adds `lshw.deb` to builtin-extensions.lst since it is a newer version than is bundled with TCL-4 (02.15 vs 02.16) and works better with TCL-5-alpha. It also makes a nice test case for importing .debs.