Refactor Logger and add Settings-UI

- Refactored logger infrastructure, so that sensors have to provide
proper timestamps for the logged data, instead of the Logger generating
a timestamp when it is logged to the file.
- Added a settings UI where active sensors and activities can be
configured

.idea/modules.xml

@@ -2,8 +2,8 @@
 <project version="4">
   <component name="ProjectModuleManager">
     <modules>
-      <module fileurl="file://$PROJECT_DIR$/SensorReadout.iml" filepath="$PROJECT_DIR$/SensorReadout.iml" />
       <module fileurl="file://$PROJECT_DIR$/app/app.iml" filepath="$PROJECT_DIR$/app/app.iml" />
+      <module fileurl="file://$PROJECT_DIR$/sensorreadout.iml" filepath="$PROJECT_DIR$/sensorreadout.iml" />
     </modules>
   </component>
 </project>