Require token address to be a contract in erc20 handler

• check if the token address is a contract in erc20 handler
• modify revert reason

All occasions of msg.sender usage replaced with _msgSender() to use with forwarders

New ChainBridge SmartContracts release that brings dozens of changes and improvements results dramatically reduction of gas usage for Deposits and Proposal Executions.
Most significant changes:

• ExecuteProposal function now called inside VoteProposal after votes threshold has been reached, so there is no need to call ExecuteProposal explicitly
• Add ERC1155Handler
• Generic handler can now validate the depositer address in the call data.
• Bridge.adminWithdraw updated to support any future handlers.
• Deposit event in the Bridge includes all the relevant info now in order to remove deposit records from the handlers storage.
• chainID renamed to domainID across all ChainBridge infrastructure.

Remove unused functions in ERC721 and ERC20 handlers.
Changes are pretty minor, but this release was not audited yet

This is the first stable release of chainbridge-solidity. This code has been audited and is ready for deployment, however caution should be taken to ensure a concrete understanding of the system before attempting to put it into production.

Changes

• Update event types (#186, #190)
• Reduce deployment costs (#167)
• Update comments (#189)

• Allow resource ID modifications #159 (#172)
• Remove adminSetHandlerAddress() (#179)
• Remove resource id from calldata (#180)
• Remove Token Counts (#177)
• Don't cancel if already cancelled (#181)
• Update proposal mapping (#184)

This is the initial release candidate of the ChainBridge solidity contracts.