Script to synchronize payments with a CSV

Adds a management script which takes a csv file name argument. Based on the values in the associated csv, transactions are deleted and fund amounts are updated.

Adds timezone configuration info (though we encourage UTC for everything).

Uses `round` when multiplying to turn dollars into cents to avoid annoying floating point issues.
I should rephrase - we have an older xls file (which is where field names and column formats came from), but not a CSV to address your concern.