Rainbow Config refactoring

[Kouprin]

We need to revisit Rainbow Config and refactor it completely.
The basic idea is to make Config filled with all default values for each required configuration and switch between the configurations.
A perfect example is https://github.com/near/near-cli/blob/master/config.js

[ilblackdragon]

Also should replace the argument stuff with yargs.

So in general something like this:

config.js:

function getConfig(env) {
    switch (env) {
        case 'mainnet':
            return {
                networkId: 'mainnet',
                nearNodeUrl: 'https://rpc.mainnet.near.org',
                ethNodeUrl: '',
            };
        case 'testnet':
            return {
                networkId: 'default',
                nearNodeUrl: 'https://rpc.testnet.near.org',
                ethNodeUrl: '',
            };
        case 'local':
            return {
                networkId: 'local',
                nearNodeUrl: 'http://localhost:3030',
                ethNodeUrl: 'http://localhost:',
                keyPath: `${process.env.HOME}/.near/local/validator_key.json`,
                masterAccount: 'test.near',
                nearEthClientId: 'client.test.near',
                nearEthProverId: 'prover.test.near',
            };
        default:
            throw Error(`Unconfigured environment '${env}'. Can be configured in src/config.js.`);
    }
}

module.exports = getConfig;

bin/rainbow-cli.js:

let config = require('../config')(process.env.NEAR_ENV || 'local');
yargs
    .strict()
    .scriptName('rainbow-cli')
    .option('nearNodeUrl', {
        desc: 'NEAR node URL',
        type: 'string',
        default: config.nearNodeUrl
    })
    .option('ethNodeUrl', {
        desc: 'ETH node URL',
        type: 'string',
        default: config.ethNodeUrl
    })
    .option('networkId', {
        desc: 'NEAR network ID, allows using different keys based on network',
        type: 'string',
        default: config.networkId
    })
    .option('masterAccount', {
        desc: 'NEAR master account',
        type: 'string',
        default: config.masterAccount
    })
    .option('keyPath', {
        desc: 'Key path for NEAR master account',
        type: 'string',
        default: config.masterAccount
    })
    .option('nearEthClientId', {
        desc: 'Account Id Ethereum Client on NEAR',
        type: 'string',
        default: config.nearEthClientId
    })
    .option('nearEthProverId', {
        desc: 'Account Id Ethereum Prover on NEAR',
        type: 'string',
        default: config.nearEthProverId
    })
    .middleware(require('../middleware/key-store'))
    .command(setupBridge)
    .config(config)
    .wrap(null)
    .argv;