Optimize var args

[nick-thompson]

Where we interface with native methods, I've used ES6 rest/spread for var args (see EventBridge, BlueprintRenderer, and NativeMethods). Duktape notes any use of the arguments object as having a major performance impact, and the babel rest/spread transform compiles to using arguments. Probably a win to be had here with the old function dispatchViewEvent(a, b, c, d, e, f) var args trick, but it's a little hard to determine without profiling.

Low priority anyway until the native methods / event interface is more stable.