Added output RCA jacks to dexter schematic

So as to make some progress, I tackled one of the things on my TODO list which can be solved independently of the current AVR dilemma: adding RCA audio output jacks to the schematic. I finished this up so now the two main obstacles to a rev2 PCB are settling on how to get the functionality that we could have if we had an extra pin, and also doing the actual PCB layout.