byte-length validator

[karel]

The current length validator validates on the string length. When you want a length restriction because, say, your database type is varchar(255), length { max: 255 } isn't good enough when the user uses multi-byte charaters (e.g. the ☃).

Suggested solution: byte-length { max: 255 } (plus an optional 'encoding' parameter to specify which charset you want to check for).