Proof of concept for using TS 2.3 plugins and transformers in tsc_wrapped

There are three ways to extend TSC:

1. Plugins that also work in an editor are written against the Language service using the plugin API introduced in https://github.com/Microsoft/TypeScript/pull/12231 These require a LanguageService wrapper around the program, and are expected to run in the tsserver.js editor helper, not in typescript.js This demo uses the @angular/language-service plugin as an example. Also see https://github.com/RyanCavanaugh/sample-ts-plugin for a simple example.
2. Plugins written only for use with tsc can skip the LanguageService and just wrap the ts.Program. This example is in tscPlugin.ts.
3. Emit transforms can mutate the AST before or after TypeScript lowers to the target language. See example in eraseDecoratorsTransform.ts.

This will let us re-write chunks of @angular/tsc-wrapped as plugins.

Here we see a diagnostic from TypeScript, a diagnostic from a plugin, and the decorator was removed by a before transform.

alexeagle@alexeagle:~/Projects/ts_plugin_prototype$ node built/runner.js
test_file.ts(1,14): error TS2322: Type '1' is not assignable to type 'string'.
test_file.ts(1,1): warning TS9999: Plugin diagnostic

alexeagle@alexeagle:~/Projects/ts_plugin_prototype$ cat built/test_file.js
"use strict";
exports.__esModule = true;
exports.a = 1;
function Cool(c) {
    return c;
}
var Foo = (function () {
    function Foo() {
    }
    return Foo;
}());