Color field: Store as RGB or HSL

[JoryHogeveen]

Currently the color field only stores HEX values. It might be nice to allow storing HEX, RGB and HSL values as well.

Storage can be done comma separated, or array (serialized or json).

Option:

static::$type . '_type'       => array(
	'label'      => __( 'Color Type', 'pods' ),
	'default'    => 'hex',
	'type'       => 'pick',
	'data'       => array(
		'hex' => 'HEX',
		'rgb' => 'RGB',
		'hsl' => 'HSL',
	),
	'pick_show_select_text' => 0,
),