Allow creating new languages that use the Monaco typescript features

[stefan-lacatus]

This PR reduces a lot of the duplicate code and adds an API to allow the user to create new languages that use the typescript workers.
In our app, the user can write JavaScript and typescript that is executed either on the sever, on in the browser. Depending on this, different extraLibs are present to provide correct intellisense.
Using this PR, we can, our app create workers for the languages that are executed server side, and reuse the standard typescript and JavaScript for the browser executed code.

[oldrich-svec]

@stefan-lacatus It seems that this code stops the worker every time there is a change:

this._configChangeListener = this._defaults.onDidChange(function () {
  return _this._stopWorker();
});

Therefore, whenever I call addExtraLib, the _configChangeListener is fired and the worker is stopped.

If I call addExtraLib fifty times, the worker gets downloaded and loaded fifty times. Is that an expected behaviour?

[stefan-lacatus]

@oldrich-svec: You are correct. See: microsoft/monaco-editor#1300
I've added a new PR that fixes this #30

[oldrich-svec]

Perfect, thanks a lot ;)