Major refactoring.

- Polyfills are now registered on a "global" reference instead of "window"
- Added a module.exports line. As a result of this and the above change, libjass can now be loaded as a node module.
- As a side-effect of this change, utility.ts must be the first file in the output. This determinism means the other files don't need to declare "use strict", and the Jakefile doesn't need to strip them.
- Renamed Iterable to LazySequence and replaced Array.ToIterable() with libjass.Lazy(Array)
- Replaced Iterator.forEach() and Iterator.toArray() extensions with LazySequence.toArray()
- Removed polyfill for parseInt that parses strings starting with 0 as octal, since libjass requires ES5 anyway and ES5 prohibits that behavior.
- As a result of the above change, String.startsWith() extension is no longer needed.
- Replaced HTMLDivElement.remove() extension with libjass.removeElement(Element)
Fixed outdated comment.