Add functionality for keywords as SIO properties

Before this commit, keywords with full namespaces would have their
namespace truncated--this commit enables the app to store fully
qualified keywords as properties.

E.g.

Before, {:foo/bar "baz"} was stored as "bar": "baz"
Now, {:foo/bar "baz"} is stored as "foo/bar": "baz"

This allows users to differentiate properties with similar names (e.g.
"item/type" and "pricing/type".