* sql/schema.sql: webfinance_invoice_rows.qtt now has 5 numbers after the
  decimal instead of 2

ALTER TABLE webfinance_invoice_rows CHANGE qtt qtt decimal(8,5) DEFAULT NULL;
* htdocs/mantis/fetchBillingInformation.php: clean
* htdocs/mantis/fetchBillingInformation.php:
* lib/WebfinanceMantis.php: allow specific time quantity