Enforce minimum transfer value per token

[stephenpdeos]

In eosnetworkfoundation/evm-bridge-contracts#29 we will be establishing a minimum token transfer value at the contract level. To improve user experience in the frontend, we should enforce these minimums prior to any actions taking place to percent unnecessary errors.

AC

• Frontend must check against the list of minimum token values to be transferred via bridge
• If a user attempts to transfer below the minimum value established for a given token, they are presented an error (still pending as to whether this will be a field validation styled error or a modal)