SVG icon inclusion support

[Zlobin Nikita]

> If I understand that right, you could do this by using the svg:use tag
> (known as a "clone" in Inkscape) to refer to an element in an external
> document. However, there would be no fallback mechanism as there is
> with icons.
> 
> http://www.w3.org/TR/SVG11/struct.html#UseElement
> 
> Regards, Krzysztof

Thanks for link. I meaned implementation scheme, comparable with code 
documentation system. I.e., when special code is written to svg property, 
supposed only for humans (properties metadata, desc).

I expect metadata to be best util for that:
http://www.w3.org/TR/SVG11/metadata.html#MetadataElement

These metadata should be for element, rendered as is only as last resort, and 
if possible - replaced by inclusion of file for referenced icon.

Another case: icon-related stuff (i mean code) could parse svg "code" for 
special tags and insert inclusions and other necessary stuff before to pass it 
to svg rendering code.

  In this case special tags may be implemented as some extension for svg, but 
in this case i don't know, will pure svg parsers smartly skip such unknown 
elements or fail on them.