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

Only reason I didn't cache this is the calculation should change if the claim changes. If any of the claim changes the calculation won't update. I think this violates the principle of least surprise, and would be annoying when using the REPL for example. Also it's not expensive to recreate the result each time in this case.