* refactor externalities::ret to take self by-value, add GasLeft enum, and alter evm::Result.
* remove unused imports, StopExecutionWithGasLeft variant
* adjust tests
* remove extraneous call to reserve
* update json_tests Ext to match new trait
* adjust executive json_test
* have evms own their memory for their entire lifetime
* make finalize API more friendly
* indentation fix
[ci skip]
* Groundwork for basic VM tracing.
* RPC endpoint for VM tracing and ser/de types ready.
* Create VMTracer trait.
* Rearchitected VM tracing to reflect existing tracing.
Should more or less work now.
* Integrated VM tracing into JSONRPC.
* Fix ethcore module tests.
* Add tests for VM tracing.
* Fix consensus test code.
* Fix mock tests.
* Added VM trace information for post-execution stuff.
* Fix max-value calls and add "creates" field to getTransaction.
* Tests for VM tracing.
* Don't implement the trait with unimplemented.
* Remove invlaid comment.
* Fix tests.
