* Add params package with exported variables generated from
github.com/ethereum/common/blob/master/params.json
* Use params package variables in applicable places
* Add check for minimum gas limit in validation of block's gas limit
* Remove common/params.json from go-ethereum to avoid
outdated version of it
* Depth check has been moved to the execution
* Pre compiled execution has been moved to the VM
* PrecompiledAddress has been renamed to PrecompiledAccount
* Code = '' if gas < len(D) * 5
* Sha3 gas 10 + 10 * len(D), rounding up 32 bytes
* Sha256 gas 50 + 50 * len(D), rounding up 32 bytes
* Ripmed gas 50 + 50 * len(D), rounding up 32 bytes
* Accounts and value transfers no longer reverted