update angular directive name and use it in demo app

[elena-p]

No description provided.

[farfromrefug]

@elena-p may i ask why you decided to rename Img to NSImg?

[elena-p]

Hi @farfromrefug,

I should have added a description, sorry.

When I tried with the Img element <Img imageUri="..."></Img> I got the following error:
Template parse errors: Void elements do not have end tags "Img"

Trying with self closing Img or without closing of the element at all, didn't generate errors, but the image was not shown.

If you prefer another name, or wish to follow the angular naming conventions, I will update the selector.

[farfromrefug]

@elena-p ok it is actually due to the fact that img is reserved and that html img is special in the sense that it does not require a end tag. So same thing in angular.

Your name is good for me