list: 'dummy' instead of 'foo' for unused argument

makes it clearer that it's construction debris
listfiles: make string-not-list as argument safe
remove: make string-safe; add "uninstall" as alias for "remove"

...because pip uses uninstall and I keep getting confused.
requires: fix & clean, allow multiple packages, clarify what it does

This doesn't report "who depends on X", rather "What does X depend on?"

Really we should have a generic "pkg.info" upper level object which
contains dependencies, name, version, etc. etc. instead of all these
little commands round tripping for their one little piece.
setup, search: pep8 formatting only; forgotten reequires output

Leaving true refactoring of Search and Setup for later. Search will be
able to be adressed more properly by planned top level pkg.info object.
Setup should be expanded to take parameter for target location, but
relies on on the total global-to-local variable name refactoring being
finished first.
update: set default mirror for x86; pep8 (still broken, #2)
fix update: only proceed 200, url exists; docs; save mirror used

close #2