[GLJS-647] Added configuration for waypoint instructions

[underoot]

• Added options instructions.showWaypointInstructions, which controls displaying of instructions for waypoints
• Added test for switching of this options
• Updated documentation

Examples

var directions = new MapboxDirections({
  instructions: {
    showWaypointInstructions: false
  }
});

var directions = new MapboxDirections({
  instructions: {
    showWaypointInstructions: true
  }
});

// or
var directions = new MapboxDirections();

[underoot]

Not sure if we need an option to turn off waypoint instructions

It was a feature request