ctrl_panel: Put plotted values into readings group

For more intuitiveness to first-time users

pytec/pytec/gui/view/ctrl_panel.py

@@ -142,11 +142,13 @@ class CtrlPanel(QObject):
                     "output", "control_method", "i_set"
                 ).setValue(settings["i_set"])
                 if settings["temperature"] is not None:
-                    self.params[channel].child("temperature").setValue(
+                    self.params[channel].child("readings", "temperature").setValue(
                         settings["temperature"]
                     )
                     if settings["tec_i"] is not None:
-                        self.params[channel].child("tec_i").setValue(settings["tec_i"])
+                        self.params[channel].child("readings", "tec_i").setValue(
+                            settings["tec_i"]
+                        )
 
     @pyqtSlot("QVariantList")
     def update_thermistor(self, sh_data):

pytec/pytec/gui/view/param_tree.json

@@ -1,5 +1,11 @@
 {
    "ctrl_panel": [
+      {
+         "name": "readings",
+         "title": "Readings",
+         "type": "group",
+         "tip": "Thermostat readings",
+         "children": [
             {
                "name": "temperature",
                "title": "Temperature",
@@ -18,6 +24,8 @@
                "decimals": 6,
                "readonly": true,
                "tip": "The measured current through the TEC"
+            }
+         ]
       },
       {
          "name": "output",