Feature/maximum width or height transformer

New ImageTransformer that resizes the layer. Accepts two Integer params: height and width. Only width **or** height will be scaled and the other dimension will be calculated to keep original ratio. If the original image is smaller than the configured dimensions the image won't be resized
I could go either way; not sure if this makes more sense as a transform param or a  "global" transform setting. worst case is in the future we add support for a transform param and use this as the default. Up to you.