Gav Wood authored Jun 16, 2016 and Arkadiy Paronyan committed Jun 18, 2016

* Gas price statistics.

Affects eth_gasPrice.
Added ethcore_gasPriceStatistics.

Closes #1265

* Fix a bug in eth_gasPrice

* Fix tests.

* Revert minor alteration.

* Tests for gas_price_statistics.

- Tests;
- Additional infrastructure for generating test blocks with
transactions.