Show Every Budget Item Due Within Window & Fix Goal Final Amount Editing
- Changes the budget item due to show every thing due within the window.
- Adds the ability to post multiple budget items of the same type.
- Implements the ability to post multiple unexpected budget items.
- Creates a dedicated ID type for a budget item that's due and another for the amount due.
- Fixes being unable to set the final goal amount.
- Adds a member function for the budget item due ID in its widget.
- Mondernises the event frequency.
Closes #20 (closed) Closes #83 (closed)