* Add new Select to filters
* get the currencies from database rather than hardcoded
* label report columns:
- If presentation currency is available in filters, use it or
- If company is available in filters, use it or
- use default company currency
* add new function - get_currency
* tweak new function `get_currency`
* add new function `convert` to convert a value to another currency
* add new function `convert_to_presentation_currency`
* clean up `get_currency` first pass
* memoise the exchange rates
* limit fetched GL entries to to_date
* check if account type is p&l or not and use appropriate exchange rate based on that
* change EXCHANGE RATE to a dict, use for memoisation
* rename EXCHANGE_RATE
* cache exchange rates and use them as needed
* add docstrings
* add presentation currency logic to financial statement reports
* move new functions from `general_ledger.py` to new module
* clean up
* PEP 8 clean up
* move function to util.py
* PEP 8 clean up
* remove presentation currency option from cashflow
* adjust currency as needed
* allow users to save presentation currency in Accounts Settings
* add new function `get_presentation_currency_list`
* refactor query_report modules with no promises
* Revert "allow users to save presentation currency in Accounts Settings"
This reverts commit 3b58a6296cf3f7b4d80ac55b03f9d5d4887b796b.
* show print page in correct currency
* Update utils.py
