Fetch account transactions

[pelson]

Add the ability to get the transactions from the IB provider's accounts.

Criteria:

• Must be able to get the transactions for a given account from any browsed location
• An account must therefore have a UID within the provider, and be able to navigate to that account's transactions
• Must handle pagination of accounts
• Each row: datetime*, ref, description, amount* (+/-), new balance ; where * is mandatory.
• Ability to stop fetching once transactions are N days older than the latest cache
• Validate the cache where overlap occurs (balance $$$ may be variant without warning due to new transactions being added that predate existing cached transactions)