confirmation email

* Checkbox selection of claimants and rep
* additional email fields (needs javascript to hide them initially) includes custom SimpleForm input
* Memoize fee_calculation
* Confirmation page/email as per Google doc

Potential NoMethodError in the case of a failed or late FGR lookup. Fix by delegating in Claim to office and allow nil. Also probably want to skip rendering that part of the view if there no office?