title: can't resolve all parameters for [object OBJECT], after ionic serve
body: <p>not sure what I'm doing wrong, but when trying to use ionic and Cordova plugins I receive the following error after ionic serve: "can't resolve all parameters for [object OBJECT],[object OBJECT],[object OBJECT],[object OBJECT],[object OBJECT],?"    </p>
  
  <pre><code>import { Component, Injectable } from '@angular/core';
  import { NavController } from 'ionic-angular';
  import { ToastController } from 'ionic-angular';
  import { File } from '@ionic-native/file';
  import { Diagnostic } from '@ionic-native/diagnostic';
  import { CameraPreview, CameraPreviewOptions, CameraPreviewDimensions} from '@ionic-native/camera-preview';
  declare var cordova: any;
  
  @Component({
    selector: 'page-home',
    templateUrl: 'home.html',
    providers: [CameraPreview, Diagnostic]
  })
  export class HomePage {
  
    constructor(
      public navCtrl: NavController,
      public toastCtrl: ToastController,
      public file:File,
      public diagnostic:Diagnostic,
      public cameraPreview: CameraPreview,
      public previewRect: CameraPreviewOptions
      ) {
      this.checkPermissions();
    }
  </code></pre>