add argument to rotate to allow user to decide rotation direction

[NicolasRannou]

https://github.com/FNNDSC/ami/blob/master/src/cameras/cameras.orthographic.js

camera.rotate(); // clockwise
camera.rotate(-1); // counter clock-wise

in cameras.ortho

  rotate( clockwise=1) {
    this.center();

    // Pi/2 rotation if camera is positions at the front of the volume
    // else -Pi/2 rotation
    let invertClock = 1;
    if(this.position.distanceTo(this._back) < this.position.distanceTo(this._front)){
      invertClock = -1;
    }

    // Rotate the up vector around the "zCosine"
    let rotation = new THREE.Matrix4().makeRotationAxis(
      this._zCosine, 
      clockwise * invertClock * Math.PI/2);
    this.up.applyMatrix4(rotation);

    this._updateMatrices();
  }