feat(*): support @NgModule

[sebholstein]

This adds a new NgModule to the project. The Module name for the
core package is AgmCoreModule. This feature is experimental.

Example:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { platformBrowserDynamic } from
'@angular/platform-browser-dynamic';
import { MyMapsProjectAppComponent } from './app/';

import {AgmCoreModule} from 'angular2-google-maps/core';

@NgModule({
      imports: [BrowserModule, AgmCoreModule.forRoot()],
        declarations: [MyMapsProjectAppComponent],
      bootstrap: [MyMapsProjectAppComponent]
})
export class AppModule {
}

platformBrowserDynamic().bootstrapModule(AppModule);

Closes #560