Handling, post markup, tax and talent fees

• Handling: a handling charge for talent and P sections that do not set their own rate. M, N and O have rates of their own.
• Post markup: added to post lines with Mark ticked, unless the section sets its own rate.
• Post tax: added to post lines with Tax ticked, unless the section sets its own rate.
• Post insurance: insurance on the post sections, all of Q to X by default.
• Talent agency fees: charged on the talent subtotal plus usage. Tick Include in the agency fee basis (usage) in a line's details to count it.
• Talent payroll service: charged on the talent subtotal.

All of these live in the budget's Settings, and each section can override them in Section settings.