Add deselect* to AbstractSelect

[howudodat]

Please add deselect functions to AbstractSelect so that I can programatically unselect an option:

  public C deselectAt(int index) {
    findOptionByIndex(index).ifPresent(this::onOptionDeselected);
    return (C) this;
  }
  public C deselectByKey(String key) {
    findOptionByKey(key).ifPresent(this::onOptionDeselected);
    return (C) this;
  }
  public C deselectByValue(T value) {
    findOptionByValue(value).ifPresent(this::onOptionDeselected);
    return (C) this;
  }