- Constant: fixed AVOGADRO typo
- MeasurementSytem: defined EPSILON for floating point precision; made ctor private
- Prefix: made prefixes a synchronized list; peta typo; used EPSILON in fromFactor() comparison
- Quantity: used EPSILON in equals() comparison; added BigDecimal case in createAmount(); checked for division by 0 in divide(double)
- UnitOfMeasure: synchronized setConversion()