ArcballControls: Fix code style.

[Mugen87]

Related issue: -

Description

ArcballControls does some strange method definitions inside its class. They look like so:

onPointerCancel = () => {

    this._touchStart.splice( 0, this._touchStart.length );
    this._touchCurrent.splice( 0, this._touchCurrent.length );
    this._input = INPUT.NONE;

};

The class does this so it can directly use the method for an event listener (to retain the this reference). However, the same pattern is applied to methods which are not intended as event listeners. This is actually breaks eslint on my system and I think it's also confusing to use arrow functions like that.

Event listeners are now normal functions like in other controls and the above pattern is completely removed from the class.