eth and erc20: enable mainnet

[chappjc]

One of the last main tasks to release ETH and ERC20 wallet support is to switch it on for mainnet and direct the v0 assets to the deployed swap contracts. They are here:

ETHSwap: https://etherscan.io/address/0x8c17e4968b6903e1601be82ca989c5b5e2c7b400#code
ERC20Swap: https://etherscan.io/address/0x1bbd020ddd6dc01f974aa74d2d727b2a6782f32d#code

Assigning myself.

For 0.6 (see the current milestone and scope here), the eth and token wallets will be fully functional with RPC providers, as will swap functionality but in a beta/experimental status initially.