Implemented `runtime.Call` which uses - unlike Execute - the given state
for the execution and the address of the contract you wish to execute.
Unlike `Execute`, `Call` requires a config.
* Moved `vm.Transfer` to `core` package and changed execution to call
`env.Transfer` instead of `core.Transfer` directly.
* core/vm: byte code VM moved to jump table instead of switch
* Moved `vm.Transfer` to `core` package and changed execution to call
`env.Transfer` instead of `core.Transfer` directly.
* Byte code VM now shares the same code as the JITVM
* Renamed Context to Contract
* Changed initialiser of state transition & unexported methods
* Removed the Execution object and refactor `Call`, `CallCode` &
`Create` in to their own functions instead of being methods.
* Removed the hard dep on the state for the VM. The VM now
depends on a Database interface returned by the environment. In the
process the core now depends less on the statedb by usage of the env
* Moved `Log` from package `core/state` to package `core/vm`.
Logs are now recorded per transactions instead of tossing them out after
each transaction. This should also fix an issue with
`eth_getFilterLogs` (#629) Also now implemented are the `transactionHash,
blockHash, transactionIndex, logIndex` on logs. Closes#654.
* PREVHASH => BLOCKHASH( N )
* State transition object uses VMEnv as it's query interface
* Updated vm.Enviroment has GetHash( n ) for BLOCKHASH instruction
* Added GetHash to xeth, core, utils & test environments
