hc: Quote shell commands properly in the log
hc: Abstract out the command name

If/when it gets renamed from "hc" to "homectl", it should be easy to
change in the docs etc...
hc: Change the enabled-list filename

enable.d is a bit misleading since it's not a directory -- call it
enabled-pkgs instead.
hc: init/upgrade code

Code to init a new homectl setup, and upgrade older setups.  Also
prettify the existing deployment-upgrade command.