131-erc-to-erc-multiple

[LiorRabin]

Added a new bridge mode ERC-TO-ERC-MULTIPLE which implements a many-to-many ERC20 bridge between two networks.

Contracts implementation can be seen here: https://github.com/poanetwork/poa-bridge-contracts/pull/140

Changes implemented:

• New watcher for the BridgeMapper contract which listens to BridgeMappingAdded events on the home network
• Other watchers updated to process events for multiple bridges (and tokens) for this new bridge mode.
• End-to-end tests for the new bridge mode
• Updated npm & docker run scripts
• Added .env examples for all bridge modes and updated documentation

[LiorRabin]

Hi @patitonar. Thanks for going over this quickly and commenting. I addressed most of the issues and would appreciate you going over this again.

[LiorRabin]

I've updated the e2e tests to work with DOUBLE_PROXY_IMPLEMENTATIONS=true after we've managed to make it work at this commit https://github.com/poanetwork/poa-bridge-contracts/pull/140/commits/06a396bd7e52b590437b66bed3c23f3bcaf97781