Make model constructors more consistent

[cammace]

We provide constructors for many of our API model classes but the parameters taken in are wildly inconsistent. For example the StepManeuver class provides two constructors:

public StepManeuver() {
  }

  public StepManeuver(String type, String modifier, Integer exit) {
    this.type = type;
    this.modifier = modifier;
    this.exit = exit;
  }

but we don't have constructors for location, bearingBefore, bearingAfter, or instruction variables. Can we get away with only having empty constructors since we now have setters for all variables @zugaldia?

[cammace]

AutoValue classes in 3.0 resolve this issue. Closing