Show nicer parsing errors in promptCurrency

[NullSoldier]

Summary

This will help parse the untyped errors from bignumber and add a new function to try and display them more cleanly.

It also now logs the reason for prompt errors.

$ fishy wallet:send

Enter the amount (balance 0.00000000): 0.000000000005
Error: fractional component exceeds 8 decimals
Enter the amount (balance 0.00000000): fisdfjgdsdsfds
Error: invalid decimal value
Enter the amount (balance 0.00000000): -4
Error: Minimum is 0.00000001
Enter the amount (balance 0.00000000): 4
Enter the public address of the recipient:

Testing Plan

Breaking Change

Is this a breaking change? If yes, add notes below on why this is breaking and
what additional work is required, if any.

[ ] Yes

[hughy]

Should we also check and render an error message if the value passed in is greater than the available balance?

[NullSoldier]

Hmmm let's get this in and see if users want that next