Allow user to intentionally reset budget allowances during rollover

Purpose:
User may not always want to update the budget allowance percentages for the coming year. This will allow them to indicated that they want to so there aren't forced to add a value

Scope:

1. Add setAllowances field to budget_rollover.json schema (type: boolean, default: false)
2. Update budget_encumbrances_rollover.sql

Approach:
Update function build_budget in the budget_encumbrances_rollover.sql

If setAllowances true set budget allowance based on the values spcified in corresponding budgetRollover item
If setAllowances false set budget allowance based on the previous years budget

Acceptance criteria:

• schema updated
• budget_encumbrances_rollover.sql updated
• API tests updated