Enable image resources from App_Resources in iOS

[vakrilov]

Image resources added in the App_Resources should be available in the application.

Currently, all files from App_Resources are copied in the Resources/icons folder inside the xCode project, but they are not included in the xCode project itself, so they are not accessible in the application.

Workaround

1. Run tns prepare ios after the images are added in the App_Resources folder. The images will be copied in the platforms\ios\<project-name>\Resources\Icons
2. Open the xCode project from the platforms\ios\ folder and add the images to the project manually: