[BUGFIX beta] SVG support for metal-views

This greatly improves SVG support in metal-view by basing the current
namespace off the contextual element. SVG components like {{somePath
should be viable with this change.
[BUGFIX beta] Use domHelper for setting attributes, allows camelCase attrs
Merge pull request #5654 from mixonic/metal-views-namespaces

[BUGFIX beta] SVG support for metal-views