bash/theme: ofb.net: stop unsetting $fmt_pwd_tail
bash: rain: add ukip()
bash/theme: set default fmt_pwd_tail
bash/theme: default $fmt_name_root
bash/prompt: move main theme to per-host section
bash/theme: foo@$host doesn't expand, so don't use that
bash/theme: unify nullroute theme, attempt 1
bash/{prompt,theme}: declarative setting for root/self prompt name
bash/theme: drop 256-color checks

Some of them were half-done (e.g. some items checked, some not), and
others are no longer neccessary as the Linux console finally understands
the 256-color codes (though it still maps them to 16 colors).
environ: stop setting $CRAWL_DIR