Add MoneyColumn and handle currency symbols etc.

[lisad]

Would a money column have two values accessible - currency type and currency amount? Would it be able to take in the valeus like "$150,000" and output two columns like "USD" and "150000"?

A simple MoneyColumn (to start with) would:

• Identify where the float/period is
• Strip non-integer characters out of the value
• wouldn't know which currency it is - just treat as a float

In the future we should probably have a CurrencyMoneyColumn that knows BOTH currency and value.