eWallet integration with the blockchain

[unnawut]

This issue tracks the progress of the integration design of the eWallet with the blockchain.

This is different from #6, #7 and #8, which are all blockchain-related, in the sense that those OIPs are more focused towards different sub-components required to connect to the blockchain, while this OIP is more focused on the high level integration design, such as:

• How local tokens and blockchain tokens will be reflected in the system?
• How new blockchain tokens can be minted from the system?
• How wallet balances from the local ledger and the blockchain be reflected in the system?
• How local wallets can interact with blockchain wallets (if possible)?
• How blockchain characteristics be reflected (or not reflected) in the system such as block height confirmation, etc?
• Validations and steps required to deploy a blockchain contract or make transactions, etc.

Note that the content of this issue is more of a scratchpad for collecting initial thoughts than an actual OIP. The actual OIP will be submitted as a pull request.

[unnawut]

Numerous tasks have been created in the eWallet to cover this.

See: https://github.com/omisego/ewallet/issues?q=is%3Aissue+label%3A%22Ethereum+Integration%22