Add image resize script for generating all icon/launch image files

This allows us to get a large base image, ie: 1024x1024 dimensions image and
generate all needed icon sizes based on the largest image.

I decided to put this in a pull request for now since I have found it very useful for white label apps, maybe Android can take advantage of it.

Instructions:

1. Make sure GraphicsMagick and ImageMagick is installed. You can do this through homebrew if you like or whatever you wish to use. After that all you need to do is run "npm install" , it will then install all dependencies needed that are stated in the package.json file.

2. Create a JSON file that let's the script know what files you want created from the base image. For example I created a JSON file called AppIconResources.json is a simple array of key/value pairs which designate the file name, file type, and size. So for example if you wanted to use it for Android, you could make a AppIconAndroidResource.JSON file and specify the name/dimensions/type you want. Then all you have to do is include the path to the JSON file and it's good to go