Rails security updates.
Update CHANGELOG.
Use bootstrap markup for reminder batch job form.
Add ReminderBatchJob#to_s overriding InvoiceBatchJob#to_s.
Add menu entries for reminder batch jobs to invoices menu.
Add proper translations for invoice and reminder batch job index titles.
Unify action links in reminder and invoice batch job views.
Add billing settings to tenant view.
Refactor Invoice.overdue to respect all grace_periods.
Add menu item to list all overdue invoices.
Fix flash messages for invoice batch job creation.
Fix flash notice for invoice printing.
Fix reminder printing and support no-CUPS version.
Fix reminder batch job printing.
Use days for periods in invoice/reminder settings.
Use AJAX calls for reminder printing in invoice view.
Add title for invoices/overdue.
Update CHANGELOG.
Switch default settings to use integer, not days/s for periods.