It makes sense to have it in bank caps too.

ntome authored Aug 21, 2020 and hydrargyrum committed Aug 26, 2020

Introduce:
- base: for CapBank, Account, Transaction and standard classes
- rate: for CapCurrencyRate
- transfer: for CapTransfer and related classes
- wealth: for CapBankWealth and related classes

To keep compatibility with existing code using base imports, bank/__init__.py
will import symbols from the subfiles.