Limit timestamp resolution

[ToniRamirezM]

Rationale

Some dapps base its logic in the timestamp and we should update it at a max interval to be defined.

Implementation

When a new TX arrives if the batch timestamp is > than the max allowed, we must close the batch, create a new one and add this new TX to the new batch.

If it is the first tx in the batch, update the batch's timestamp to time.now()

Use a new config parameter: timestampResolution

Remove current parameter to close a batch due to a timeout.
Take into account this timestamp for gas estimation and eth_call: use time.Now() if block is not forced.