Returns the current environment
@returns {Object} Contains contract addresses, Hermez API and Batch Explorer urls
and the Etherscan URL por the provider
Sets an environment from a supported environment configuration or from a custom environment object
@param {String} env - Supported environment name
@param {String} web3ApiKey - Web3 api key
@param optional {EnvParams} envParams - Custom environment object, only used when env value is 'custom'