Introduce prefixes in bindAll

[goshacmd]

Make slate.bindAll accept an optional argument of prefix map.

// simple mapping
slate.bindAll({ "esc:ctrl;alt" : S.op("relaunch") });

// with prefixes
slate.bindAll({ layoutKeys: "ctrl;cmd" }, {
  "l:#layoutKeys": laptop,
  "t:#layoutKeys": thunderbolt,
  "b:#layoutKeys": twoMonitor
});

[lunixbochs]

The method I use in reslate for this uses nested objects like so:

slate.bindAll({
    'ctrl;cmd': {
        'l': laptop,
        't': thunderbolt,
        'b': twoMonitor
    }
});