Added option to evaluate length in UTF-8 bytes

Set the utf8Bytes boolean to "true" (defaults to "false") to compare the min/max string length in UTF-8 bytes to facilitate validation for database inserts.  Leaving the boolean as "false" or not configuring it, is compatible with existing functionality of this validator so this shouldn't affect anyone's existing usage of this validator.

This code is based on that by Mike Samuel posted at the following web address on 4/01/2011: http://stackoverflow.com/a/5515960