[feature] Extending Ethereum-SONs to support ERC20 tokens

Right now the Ethereum-SONs supports moving of ETH token across the blockchains. This functionality must be extended to support ERC20 tokens as well. While we need the ERC20 support for all tokens eventually, we need to start with a white listed and pre approved set of 3 tokens. If additional tokens are to be supported, the respective token owners must created a proposal to add support for the token. This verification mechanism is introduced to make sure that no spam/junk assets are included and there are no attacks against tokens thats moved from other Layer2 or Layer1 solutions in the future. Any end user can create a proposal to submit a token on a supported chain and the witnesses must then approve the proposal to include or ignore the token. [Can we have either manual method or a longer proposal approval/disapproval time to give time for witnesses to manually approve the requests ? Any other methods ? ] There must be a mechanism to list/unlist tokens as the network may need to ignore tokens from time to time.

Tokens from Layer2 Solutions (Hive-Engine, TribalDEX, SPK Honeycomb & others)

For the above mentioned tokens, we will have to consider the scenario of the token originally being available in the networks [both Peerplays & Ethereum] and ideally we must be supporting tokens which are already present in these supported chains. (additional discussion needed during design phase).