Removed old song processing code. Uses promsise now.
Started new upload UI.
Added success and failure states to song upload statuses.
SongAdd remove event triggered when removed via reset.
Removed old upload scripts.
Added new jquery file uploader. Server tells client of add status.
Added config option debug_socketio.
Song uploading front-end functional again.

Added file upload size check.
Drag & Drop works.
Mapped display values for upload status.
Created promise-based fs.exists function in fs.js.
Reimplemented song processing and enqueueing.

There's a bug where the queue gets randomly shifted, and
songs are enqueued in the wrong position.

Also converted more code to use promises instead of callbacks.
Simplification of song process promise logic.

Song process job IDs are incremental instead of random now.
Fixed song thinking it's being reordered when we drop an upload on it.

Also improved QueuedSong backbone model's getLogName().
Queue automatically repairs song orders when fetching from db.
Whitespace correction.
Removed unnecessary event forwarding, fixing double song order update.

I didn't realize that model events bubble up to their collection
automatically.
Merge branch 'new-upload', reimplementing song adding and enqueueing.

Made entirely new file uploading UI using backbone like everything else.
File uploading uses jquery.fileupload instead of dropzone.
Replaced old song proccessing code with new promise-based logic.
Front-end fixes to eliminate accidential event triggers.
Queue automatically repairs song orders when fetching from db.
Added config option debug_socketio to toggle showing noisy socket.io logging.
Created an fs.exists() that returns a promise.