Add "set" command to setup menu, and add optional argument to "show".

Squashed commit of the following:

commit 4243a0bb89de2f850606c623aac6a5b583c333ae
Author: John Stäck <stack@spotify.com>
Date:   Thu Mar 7 09:28:16 2013 +0100

    Undo change to system.pde, not needed.

commit dae2dbbbd6e13621fccc1d0a221aae8d83240417
Author: John Stäck <stack@spotify.com>
Date:   Wed Mar 6 22:47:50 2013 +0100

    Remove leftover bits of old menu setup

commit ccefc8fe0d237364b06a1478348f8552720d7598
Author: John Stäck <stack@spotify.com>
Date:   Wed Mar 6 22:40:30 2013 +0100

    Roll the param menu into setup.

commit c61dad17bf32a3080d8eca2389c6e25f98767545
Author: John Stäck <stack@spotify.com>
Date:   Wed Mar 6 08:08:42 2013 +0100

    Make the param menu a compile-time option, by defining PARAM_MENU

commit 0f35c4e88ec7aba5035b4880e9994e4783da75a9
Author: John Stäck <stack@spotify.com>
Date:   Wed Mar 6 07:57:22 2013 +0100

    Use find(), which works well.

commit 3b81b29597fcee49193330d7b6d3f3aed99a476c
Author: John Stäck <stack@spotify.com>
Date:   Tue Mar 5 07:57:33 2013 +0100

    Whitespace fixes

commit 6b9ccc5fe1de1e40a24eb9ff89006b9bd80e3662
Author: John Stäck <stack@spotify.com>
Date:   Tue Mar 5 07:28:20 2013 +0100

    Add cli menu to change any parameter.