Store amount when the funding transaction is sent

[escottalexander]

Currently when the funding transaction is sent we add 15-20% so that we make sure it is enough if gas prices move against us while the user is signing the recovery transactions. This could be made more efficient if we use the funding amount as a reference for the gas price of each recovery transaction. This way the user should never send more than would potentially be used and in the other case they can never create transactions that potentially use more gas than is given.

All this logic is in useRecoveryProcess and useGasEstimation I believe.