Allow value decorator to specify many pairs of annotations.

Lets say you want to annotate an event with two attributes.

Right now you would have to use two value decorators:

{ value("foo","fooval") =>

{ value("bar","barval") => sink }

}

A bit verbose but workable. It would b enice to allow multiple values to be set by using this slightly terser notation:

{ value("foo", "fooval", "bar", "barval") => sink }