current_tariff and previous_tariff moved from application_helper to tariff_helper
All tariffs now sorted by start_date ( Tariff#index)
Removed orphaned previous_report calculation. Replaced with helper method call.
Added edit and remove tariff buttons. Edit button open edit tariff form. Remove button doesn't work yet.
Added tariff removing.
Added forgotten bootbox.js that was used to show confirmation dialog when removing a tariff.