Control Panel: Better steps and units in paramtree

- Step r0 by 100 Ohms instead of 1 Ohm
- Step b by 10 K instead of 1 K
- Prefix temp_swing with +/-

pythermostat/pythermostat/gui/view/param_tree.json

@@ -179,7 +179,7 @@
                "title": "R₀",
                "type": "float",
                "value": 10000,
-               "step": 1,
+               "step": 100,
                "min": 0,
                "siPrefix": true,
                "suffix": "Ω",
@@ -195,7 +195,7 @@
                "title": "B",
                "type": "float",
                "value": 3950,
-               "step": 1,
+               "step": 10,
                "suffix": "K",
                "decimals": 4,
                "compactHeight": false,
@@ -351,8 +351,7 @@
                      "type": "float",
                      "value": 1.5,
                      "step": 0.1,
-                     "prefix": "±",
-                     "format": "{value:.4f} °C",
+                     "format": "± {value:.4f} °C",
                      "compactHeight": false,
                      "pid_autotune": "temp_swing"
                   },