Unidirectional patch updates

[Beanow]

Something I noticed BTS has but FxFloorboard and the Android Editor don't have, is updating the interface when parameters are changed on the amp.

At the moment I already have:

• The ability to apply a sysex message as-is to a patch, updating the in-memory patch (In memory patches #3 + SysEx messages #4).
  Similar to an Action.
• Ways to query the in-memory patch data (In memory patches #3).
  Similar to a Store.

It doesn't take a lot of additional work to implement a unidirectional dataflow similar to things like flux.

The simple implementation would be:

• Adding a callback to subscribe to change notifications. Which will make the UI render again.

Ideally though we should extend this:

• Create a few abstractions to do more specific subscribing, letting you reduce the number of queries and render only part of your UI.
• Either expose a copy of the data to the callback, or implement the dispatcher model to guarantee the data is in a consistent state and immutable while your UI is still rendering.