[Research] Investigate the Interactive Brokers CVS export

[leppa]

Things that must be done before Interactive Brokers format plugin can be implemented:

• Investigate what CSV format does IBKR offer.
• Identify quirks and limitations of the format.
• Define the optimal export options (columns, transaction types, etc.), when available.
• Document and update [Format Request] Interactive Brokers #11 with the findings.