Feature request: support duplicating transactions

[jsumners]

At the moment, the manual entry of many similar transactions, e.g. adding records of interest received, is very cumbersome because there is no way to duplicate an existing transaction. It would be very helpful if we could:

1. Duplicate a transaction
2. The new transaction immediately opens to the "edit" pane
3. Adjustments can be made, e.g. change the date and/or amount
4. The "save" button will record the new transaction