Resolved some bugs in the miner

* TODO nonce error sometimes persists
* Fixed mining on wrong blocks
* Fixed state error & receipt fail

core/chain_manager.go

@@ -392,7 +392,7 @@ func (self *ChainManager) InsertChain(chain types.Blocks) error {
 
 				self.setTotalDifficulty(td)
 				self.insert(block)
-				self.transState = state.New(cblock.Root(), self.db) //state.New(cblock.Trie().Copy())
+				self.transState = state.New(cblock.Root(), self.db)
 
 				self.eventMux.Post(ChainEvent{block, td})
 			}