Feature detection for CSS3 Gradients with ANGLES

Left comments in the code, however just in 2 words: it's not enough to have general css gradients detection as there are some browsers (like Blackberry) that DO support -webkit-gradient but DON'T support -webkit-linear-gradient which in case you use ANGLES for your gradient means your gradient will not work. So there SHOULD be separate feature detection, and that is what I added. It works for me like a charm so hopefully it will be helpful to others.