Rewrite the Alda REPL as part of the Java client

[daveyarwood]

Right now, alda repl just uses Java-Clojure interop to run (alda.repl/start-repl!) which means you have to wait for the Clojure runtime to load, the MIDI system to initialize, and a new Alda score to be initialized.

The REPL is really just an interactive version of the Alda client, so now that we have a client, I think we should re-implement the Alda REPL in terms of the client. This would carry two major benefits:

1. Immediate start-up, no waiting for the Clojure runtime.
2. You would be interactively editing Alda scores running on existing servers. This would give you the flexibility to go back and forth between editing scores on the command-line (in your editor, etc.) and hopping into the Alda REPL to edit the same score.

Hopefully this won't be too difficult. The Alda client already does most of the things we need the REPL to do, and most of them are functions in the AldaServer class. Basically we'll just be translating the JLine interface into Java and have it call functions in the AldaServer class.

[daveyarwood]

Moved to alda-lang/alda-client-java#1.