Send accepted any amount parseFloat() read as above zero, so "1e-3",
"1abc" and an amount with more decimal places than the token has reached
ConfirmTx, which then refused them. isValidAmount() in
src/shared/txValidation.js is now the one check: Review and Max on Send
call it with the token's decimal places, and validateTransfer() calls it
for ConfirmTx, which now also refuses a zero amount and a token amount
with more places than the token has.
Model: opus-5-5
