Separate out units

[atmoos]

Separated out units into its own .csproj.

Necessary conditions:

• multiplicative operators on measures are self sufficient.
  • implemented in Multiplicative measures #26
• Serialization can be parametrised with assemblies that contain units.
  • implemented here.

Improved implementation of:

• Pow() functions
• Simplify() functions

Left the following frequently used units in the quantity library:

├── Si
│   ├── Ampere
│   ├── Candela
│   ├── Derived
│   │   └── Celsius
│   ├── Kelvin
│   ├── Kilogram
│   ├── Metre
│   ├── Metric
│   │   ├── Hour
│   │   ├── Litre
│   │   └── Minute
│   ├── Mole
│   └── Second
└── Imperial
    ├── Length
    │   ├── Foot
    │   ├── Inch
    │   └── Mile
    ├── Mass
    │   └── Pound
    ├── Temperature
    │   └── Fahrenheit
    └── Volume
        └── Pint