fix(ngInclude): correctly add non-html namespaced template content

It is now possible for ngInclude to correctly load SVG content in non-blink
browsers, which do not sort out the namespace when parsing HTML.

/CC @tbosch / @IgorMinar

Closes #7538
Could change `detectNamespaceForChildElements` to use `var node = (parentElement && parentElement[0]) || parentElement;` rather than `parentElement && parentElement[0]`