Improve CSV importer
Recently one of my bank changed their CSV output so that the amount is accompanied by a second field that given the content identifies the amount as debit or credit. The current CSV importer is not capable of handling this scenario and needs some additional UI to handle this (not so uncommon) case. The UI has been cleaned up a bit in the same context. And while I was at it, I added the capability to extract the balance from one of the columns if present and also added clear buttons to reset each item individually.