Parse quantity and unit from string

[angularsen]

Add Parse(string) to unit classes. Should handle integers, decimals and different variations of whitespace and multiple case-sensitive abbreviations per unit.

Examples:

• 1kg, 1 kg => 1 kilogram
• 1l, 1L, 1 l, 1 L => 1 liter

Volume.Parse("1L") == Volume.FromLiters(1)

[angularsen]

Disregard commit 462420d, it was a mistake.