Add temporary StaticSecure method to explicity fetch secure asset paths

Our current implementation of `Static` assumes that your entire environment is secure to return secure paths. This doesn't enable us to change the paths on a per route/action or individual asset basis, which we require for the new embed work.

After discussing with @gklopper this is a temporary solution until we discuss with Level3 the possibility of serving both protocols over the same host, which in-turn would negate the need for any of this and we can just use a single protocol relative path.

/cc @mattosborn