Release 1.6.0

• Add Qty.getUnits to return available units of a well-known kind
• Add Qty.getAliases to return every alias of a specific unit
• Allow to initialize a quantity with scalar and units as separate arguments
• Rename memory kind to information
• Add information_rate kind
• Accept Wh and Ah as units
• Fix hang when using water height pressure units
• Add plural for fluid ounce
• Fix amu and dalton definitions
• Add tb as tablespoon alias
• Add plural for information units
• Minor fixes or improvements