Draft: Computer (final)

Main purpose: Split responsibility of Money object and provide solution for basic arithmetics with precision. Also to remove schizophrenic data interface of Money. All parameters are expected to be numbers without any adjustments or instances of Money.

For backward compatibility all comparisons and arithmetic is done by first available library (GMP > BCMath > native) with precision to 8 decimal place which should be enough for divisions since default currencies have 3 decimals maximum.

Computations are done like this:

```php
$computer = new MoneyComputer(new Calculators\GmpCalculator(/* precision */8));
$computer->add(1, 1); // '2'
$computer->multiply(new Money(10000, Currency::get('CZK')), 1.21); // Money(12100, Currency('CZK'))
```

Implemented functions: add, divide, multiply, subtract, compare, equals, largerThen, largerOrEquals.
Rest of comparison functions can be added with ease.
*Advanced functions are not implemented and I have no desire to add them. I think they would overreach purpose of this library and bring me a headache.*

Note: *MoneyComputer is splitted from Computer to show the difference from basic implementation without Money.*