feat(ngSanitize): accept SVG elements and attributes

SVG elements and attributes are now accepted and sanitized by ngSanitize.

Closes #9578
It is xlink:href -- please send a pr, although I still need to figure out what is causing the failures and revert. I'll get to that in an hour or so.

> On Oct 23, 2014, at 7:43 PM, Georgios Kalpakas <notifications@github.com> wrote:
> 
> In src/ngSanitize/sanitize.js:
> 
> >  
> >  //Attributes that have href and hence need to be sanitized
> > -var uriAttrs = makeMap("background,cite,href,longdesc,src,usemap");
> > -var validAttrs = angular.extend({}, uriAttrs, makeMap(
> > -    'abbr,align,alt,axis,bgcolor,border,cellpadding,cellspacing,class,clear,'+
> > +var uriAttrs = makeMap("background,cite,href,longdesc,src,usemap,xmlns:href");
> Did you by any chance mean xlink:href ?
> Also, should we add action to the list
> (based on https://wiki.whatwg.org/wiki/Sanitization_rules#Attributes_whose_value_is_a_URI) ?
> 
> —
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