Moved execution from vm to chain.

This moves call and create to the specified environments. Vms are no
longer re-used. Vm uses environment's Call(Code) and Create in order to
execute new contracts or transfer value between accounts.

State transition now uses the same mechanism described above.

state/state_object.go

@@ -276,15 +276,14 @@ func (c *StateObject) Init() Code {
 	return c.InitCode
 }
 
-// To satisfy ClosureRef
-func (self *StateObject) Object() *StateObject {
-	return self
-}
-
 func (self *StateObject) Root() []byte {
 	return self.State.Trie.GetRoot()
 }
 
+func (self *StateObject) SetCode(code []byte) {
+	self.Code = code
+}
+
 //
 // Encoding
 //