"Gratuituous metaprogramming" cc @threedaymonk 😂
ClaimFeeCalculator

Original behaviour was incorrect. I have amended it to what I now understand
as correct and I am waiting on Helen to confirm.

Changes:

 - If there is one claimant and they are applying for remission, the remission
   amount is 100% of the application fee
 - Simplification of the specs.