Added a 'Signal Converter' preset

As a branch of the default configuration, I added this to help those less-modularly-inclined visualize and convert the signals coming out of Sonic Pi to something that may be considered useful within a modular domain, and especially for Poly Grid using some nifty phase converters / counters.

While not exactly "modular synthesis 101" (I have multiple video series on the topic!) or even Poly Grid 101, this can at least get you up and running with a few neat ideas sketched out, so that you can build some fantastic rigs and make some great music on top of it all.

There are also labels and comments galore, hopefully to help you understand what's going on a little better!