Merge multiple arrays into one with unique items.

{@link Ext.Array#union} is alias for {@link Ext.Array#merge}

@param {Array} array1
@param {Array} array2
@param {Array} etc
@return {Array} merged
function() {
            var args = slice.call(arguments),
                array = [],
                i, ln;

            for (i = 0, ln = args.length; i < ln; i++) {
                array = array.concat(args[i]);
            }

            return ExtArray.unique(array);
        }