* no longer export action_params
* remove transaction, header, receipt re-rexports from common
* remove env_info and builtins re-exports from common
* remove everything but util export from common
* replace common usages with util, remove module
* add a prelude module for ethcore-bigint
* Spliting gasometer out of interpreter
* Choosing right gas calculations implementation based on supplied gas
* Moving verification out of gasometer
* MemGasCost benchmark.
Conflicts:
ethcore/src/evm/benches/mod.rs
* Some simple benchmarks
* Benchmark for simple loop
* Calculating gas_for_memory only when it's actually needed
* Removing superfluous newline [ci skip]