SVGLayer becomes pixelated when zoomed

[sebastianludwig]

Steps to reproduce the issue

1. Use the following snippet as viewDidLoad in IcelandicViewController
2. Run the demo and choose "Icelandic"
3. Zoom in

override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        
        let svgURL = Bundle.main.url(forResource: "iceland", withExtension: "svg")!
        let svgLayer = SVGLayer(contentsOf: svgURL)
        icelandicView.layer.addSublayer(svgLayer)
        
        svgLayer.bounds = CGRect(x: 0, y: 0, width: svgLayer.preferredFrameSize().width, height: svgLayer.preferredFrameSize().height)
        icelandicView.frame = svgLayer.bounds
        
        let scrollview = UIScrollView(frame: view.bounds)
        scrollview.maximumZoomScale = 50.0
        scrollview.minimumZoomScale = 0.5
        
        scrollview.contentSize = svgLayer.bounds.size
        
        scrollview.delegate = self
        
        scrollview.addSubview(icelandicView)
        
        view.addSubview(scrollview)
    }

One great advantage of vector images is, that they can be zoomed without blurring/pixelating. However PocketSVG/SVGLayer does not yield this benefit, because rasterization is enabled.

The origin of this goes back to the implementation of SVGImageView in 2014, unfortunately without explanation why rasterization was enabled.

Do you guys remember? If so, could you maybe a comment about it in the readme? Otherwise I suggest leaving shouldRasterize on its default value NO.

With rasterization:

Without rasterization:

[fjolnir]

I made it on by default for performance reasons. It's easy to disable if needed.