Initial implementation of texture generator

In ViewController:

• New `destImage` getter will return the `_destImage` if set, otherwise creates the image via a CGImage and CGDataProvider that trigger the image generation.
	• New logic in `viewDidLoad` and `pointsDidChange` to trigger image generation/regeneration.
		» Instead of the temporary patch of setting the `_destImage` to equal the `_srcImage`!
• `genDestImageBytesAtPosition` is a CGDataProviderGetBytesAtPositionCallback-conforming function that — for now — simply sets all pixels to transparent black.
	» Trying to figure out how to best use CGDataProviderCreateDirect() API.  It seems to just ask for all the data at once which seems kinda pointless.  The docs say that this approach is good for JIT delivery of image data.