Add attribute? method (like Foo.new.whatever?) returns true if it has
been set to anything, false otherwise. False if not set *and* there is a
default.

The intent is to provide "Has the user provided a value here?"

This code may not stay; an example use case is for the runit platform
where it uses "/service" by default except on debian which (sigh)
patches it to use "/etc/service". We'd want a default value of /service
but be able to switch in /etc/service if targeting debian and no
explicit value is provided... meh
Move shell-related-quotey-functions to Base.

Should move to a module eventually..
Refactor runit support to use attributes.

Also modify template to experiment with building command line settings
in the shell.