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/gradle.xml

@@ -3,9 +3,8 @@
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
-        <option name="distributionType" value="LOCAL" />
+        <option name="distributionType" value="DEFAULT_WRAPPED" />
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="gradleHome" value="$APPLICATION_HOME_DIR$/gradle/gradle-2.10" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />