Block header changed & console miner control

* miner control moved to `admin.miner`
* miner option to set extra data
* block extra now bytes

miner/miner.go

@@ -13,7 +13,6 @@ type Miner struct {
 	worker *worker
 
 	MinAcceptedGasPrice *big.Int
-	Extra               string
 
 	mining bool
 	eth    core.Backend
@@ -58,3 +57,7 @@ func (self *Miner) Stop() {
 func (self *Miner) HashRate() int64 {
 	return self.worker.HashRate()
 }
+
+func (self *Miner) SetExtra(extra []byte) {
+	self.worker.extra = extra
+}