cmd/evm, core/vm, test: refactored VM and core

* 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`.

core/events.go

@@ -20,8 +20,8 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
 )
 
 // TxPreEvent is posted when a transaction enters the transaction pool.
@@ -42,23 +42,23 @@ type RemovedTransactionEvent struct{ Txs types.Transactions }
 // ChainSplit is posted when a new head is detected
 type ChainSplitEvent struct {
 	Block *types.Block
-	Logs  state.Logs
+	Logs  vm.Logs
 }
 
 type ChainEvent struct {
 	Block *types.Block
 	Hash  common.Hash
-	Logs  state.Logs
+	Logs  vm.Logs
 }
 
 type ChainSideEvent struct {
 	Block *types.Block
-	Logs  state.Logs
+	Logs  vm.Logs
 }
 
 type PendingBlockEvent struct {
 	Block *types.Block
-	Logs  state.Logs
+	Logs  vm.Logs
 }
 
 type ChainUncleEvent struct {