stepconf -refactor to use GTK Builder and Notebook

Gnome Druid is broken and discontinued.
broken up into more files for ease of adding functions/pages
Should work just as original here aside from no more README
README was empty anyways
stepconf -have stepconf reset the axis defaults on unit change

now when you change the units stepconf will reset the xyz axes to
either metric or imperial - changing only the variables that make sense.
stepconf -make the navigation buttons direct the user

change to text labels for fwd and back buttons.
change it from 'start' to 'fwd' to 'done' as required.
add an icon check mark to 'done' for fun.
stepconf -add a second parallel port signal selection page

can't select step or direction signals - not sure if it's
possible to have stepper drive pins on two ports.

axis test needs some adjustment for seconf port.