ERC20 Precision API for Clients
We need an API call to get the token name and decimals using the contract address for clients like `swapcli`, which need that info to display the token information correctly. As part of the work, we should review the code to make sure we do proper validation on the number of decimals throughout the flow.  For example, we should reject provides amounts that use too many decimal places. We also should look into rounding in the proper direction when computing min/max values for the user in the provided token.