* [contracts] ContractInteractions.new() now requires account parameter
* [cli] Only perform Ethereum interactions when --eth-account is specified
* [cli] Add --persistence option that is disabled by default
* [cli] Use Option for ethDeployment parameter
* [node] Better error reporting when Ethereum node cannot be reached
also fix a discrepancy where cli option `--cache-size` is documented as
`0 disables the cache` in `codex/conf.nim`, but previously the value `0` would
result in a cache being constructed with default parameter values for
`CacheStore.new()`
Closes#180
Michael Bradley, Jr
markspanbroek