Import SimpleFIN transactions from the end of last month

[james4141]

When importing transactions from SimpleFIN, the default behavior is to import all transactions for all days in the current month. This requires the user to remember to flip back to the previous month, several days after the new month has begun, in order to catch any old transactions that hadn't posted yet.

Proposed solution: Import transactions since the last Sync/Import date, so long as it hasn't been more than 30 days ago; else revert to the old logic of current month only. Doing it this way should prevent clobbering up the budget in the case a user had stopped using SimpleFIN for a while and recently restarted.