Added load Image from URL

[AlphaRex12]

Load a image from a URL!

[SebastienGllmt]

I don't like this because it's a case of DRY (http://en.wikipedia.org/wiki/Don%27t_repeat_yourself) where we're creating a copy of a previous constructor we already have but with a single variable change. If you wanted to add this, I suggest you make one call the other.
i.e. URL constructor turns it into a string and calls the String constructor
String constructor turns into a URL and calls the URL constructor

That makes that if we want to change how the Texture object is constructed, we don't have to change the same code in multiple places.