SlotMachine up & running.

After many workarounds, I was able to provide an implementation for
the SlotMachine application. Honestly, I don't know if it's because of
the current application or Yampa is really annoying to deal with.

The major problem was the read-and-then-write situation. For example,
the credit. First, you have to read it, in order to determine if the
player can play or not. Then, you have to update it (spend credit or
win prize). Well, this was impossible to deploy, so I have to add many
workarounds (for instance: negative credits).

In general, everything is quite weird, because you have to think in
your application as a circuit, where some components can be stateful
(accumHold) in a strange way. I think that the switching has to
provide many facilities and I have to read deeper in that line to
improve my skills with this technology.