Millisecond precision Time, Timestamp, and DateTime for MySQL

As of MySQL 5.6.4, millisecond and microsecond precision has been properly supported for the Time, Timestamp, and DateTime fields (see http://dev.mysql.com/doc/refman/5.6/en/fractional-seconds.html).

This PR allows Liquibase to properly recognize types such as `TIMESTAMP(6)`. Previously, it would ignore the parameter and use just `TIMESTAMP` in the output. Now it will read the parameter and properly put out `TIMESTAMP(6)` or similar.

Types such as `TIMESTAMP` will still work correctly; the parameter is not required.