Add missing/change definition in durandal/durandal.d.ts

- Make applicationHost parameter optional in setRoot
- Add missing activeRoute definition
- Add missing useConvention definition
- Add missing handleInvalidRoute definition
- Change mapRoute definition so you can pass an URL with all the other
parameters as you will usealy do or you pass a RouteInfo object without
having to give it any other parameter. moduleId, name and visible are
now optional.