Return data implementation

[hilmarx]

PR includes:

• Old Rinkeby deployments
• Some new scripts for the UI, which are already redundant and have to be updated
• Changes in Provider Modules to use GelatoMultiSend
• GelatoMultiSend.sol
• Changes in all actions to accept and decode data
• Updated Tests
• Made ActionWithdrawBatchExchange modular and excluded transferFrom action from it
• Updated ERC20Transfer action to ActionTransfer => allows proxies to send ETH and ERC20s
• Deleted all contracts with Fees
• Implemented FeeHandler contract to handle fees for all other contracts
• Deleted old implementations of Fee Contracts

[gitpusha]

Merging into master but we should take a look at

buidler/tasks/deploy/task.setupGelato.js

It looks outdated