Added phetioInputEvent class, see https://github.com/phetsims/tandem/issues/67 and https://github.com/phetsims/phet-io/issues/1388
Added phetioInputEvent class, see https://github.com/phetsims/tandem/issues/67 and https://github.com/phetsims/phet-io/issues/1388

phetsims/joist,phetsims/joist,phetsims/joist