fixed several potential nullptrs

code cleanups
logging enhancements (memory/cpu)
reduced log footprint (diskspace)
fixed some potential layout issues
added comments

app/src/main/AndroidManifest.xml

@@ -2,7 +2,10 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="de.fhws.indoor.sensorreadout">>
 
+    <!--
     <uses-feature android:name="android.hardware.type.watch" />
+    -->
+
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
     <uses-permission android:name="android.permission.BLUETOOTH" />