The problem was that the BigInt lib did not handle decimals at all. `divMod` only let the remainder be what is after the dot. So I created my own divde and multiply methods to move the dot depending on the number of decimals
Add gas estimate for sticker pack purchase.
Update transaction for sticker pack purchase.
Add GasValidator component which validates gas is selected correctly and displays an error message if not. This component is not visible until it is not valid (at which point the valdiation error message is displayed).
In a future PR, need to:
1. estimate gas for token txfer (sendTransaction) via a normalised method for estimating gas for EthSend
2. move sticker pack purchase to use an EthSend object so gas can be estimated and tx sent