Fixed a few issues in the miner and updated hash rate title

* Sometimes old nonces were set by "old" agents
* Added the hash rate to the miner

cmd/mist/assets/qml/main.qml

@@ -289,6 +289,7 @@ ApplicationWindow {
             styleColor: "#797979"
         }
 
+	/*
         Label {
             //y: 6
             objectName: "miningLabel"
@@ -307,6 +308,7 @@ ApplicationWindow {
             anchors.right: peerGroup.left
             anchors.rightMargin: 5
         }
+	*/
 
         ProgressBar {
             visible: false
@@ -1101,4 +1103,4 @@ ApplicationWindow {
                  addrField.focus = true
              }
          }
-     }
+     }