Popups done, Readout Screen prepared, Small fixes

biogascontrollerapp/gui/main/main.py

@@ -0,0 +1,25 @@
+from kivy.uix.screenmanager import Screen
+from kivy.lang import Builder
+
+from lib.com import Com
+
+
+class MainScreen(Screen):
+    def __init__(self, com: Com, **kw):
+        self._com = com;
+        super().__init__(**kw)
+
+    def start(self):
+        pass
+
+    def end(self):
+        pass
+
+    def reset(self):
+        pass
+
+    def back(self):
+        pass
+
+
+Builder.load_file('./gui/main/main.kv')