* Initial implementation of era1 + export + verify
Initial implementation of era1 + export and verify command in the
existing eth_data_exporter.
* Quick verify version to test with geth created era1 files
* Add Era1File object and getter for specific block tuple
* Add getAccumulatorRoot and update AccumulatorRoot type name
+ clean-up of some comments.
* Implement BlockIndex based verify + additional helper calls
+ fix bug for reading last (incomplete) Era1 file
* Fix init BlockIndex offsets for last era + extra check on reading
* Remove duplicated e2store code