Support for attributes on <use> and importNode usage

[timeiscoffee]

• Wrapping <use> embeds in <g> and copying relevant attributes to <g> (Based on if use element has additional attributes, they will be copied to a new group element #122)
• Use document.importNode if available, fallback to cloneNode otherwise (Based on Using importNode instead cloneNode. #113)
• Updating README to href from xlink:href
• Relaxing ESLint rule for max-param

[Eschon]

I just tried this out and found a few small problems with it.

First I realized that it doesn't solve #145 completely. @BenDTU mentioned the x and y attributes. Those are copied to the g tag but it doesn't support them. This was also a problem in #122 which I didn't notice.
Fixing this should be possible by just checking for x and y attributes and putting them into a transform="translate(...)"

I also found another interesting Problem. If I have multiple use tags linking the same icon they all get the attributes from the last use tag linking it.

Aside from the mentioned problems it works for me.

[timeiscoffee]

@Eschon thanks for giving it a go.

Re: x, y, I think that should be tackled on as a separate PR.

Re: multiple <use> tag, could you clarify on this? I just tried with copy pasting a <use> tag with same href and changing the attribute, and they seem to preserve their own attributes after fill.

[Eschon]

Sorry it took me such a long time to get back to this.
I created a small test case that shows the problem. You can find it here:
https://github.com/Intermaps/svg4everybody-test

[andi1984]

What is about this PR? I would love to see it in!