PreferenceList: let summary be set by Android.

Some preferences used customized summaries - these were also removed.

src/main/res/xml/settings.xml

@@ -35,10 +35,12 @@ limitations under the License.
         android:key="@string/settings_advanced_key"
         android:persistent="false"
         android:title="@string/settings_advanced" />
-    <Preference
-        android:title="@string/about_preference_title">
-        <intent
-            android:targetPackage="@string/applicationId"
-            android:targetClass="de.dennisguse.opentracks.AboutActivity" />
-    </Preference>
+    <PreferenceCategory android:title="@string/about_preference_title">
+        <Preference
+            android:title="@string/about_preference_title">
+            <intent
+                android:targetPackage="@string/applicationId"
+                android:targetClass="de.dennisguse.opentracks.AboutActivity" />
+        </Preference>
+    </PreferenceCategory>
 </PreferenceScreen>

src/main/res/xml/settings_chart.xml

@@ -18,6 +18,7 @@ limitations under the License.
     <ListPreference
         android:defaultValue="@string/chart_x_axis_distance"
         android:key="@string/chart_x_axis_key"
+        android:summary="%s"
         android:title="@string/settings_chart_x_axis" />
     <PreferenceCategory android:title="@string/settings_show">
         <CheckBoxPreference

src/main/res/xml/settings_recording.xml

@@ -18,37 +18,46 @@ limitations under the License.
     <ListPreference
         android:defaultValue="0"
         android:key="@string/voice_frequency_key"
+        android:summary="%s"
         android:title="@string/menu_voice_frequency" />
     <ListPreference
         android:defaultValue="0"
         android:key="@string/split_frequency_key"
+        android:summary="%s"
         android:title="@string/menu_split_frequency" />
     <ListPreference
         android:defaultValue="@string/settings_recording_track_name_date_iso_8601_value"
         android:key="@string/track_name_key"
+        android:summary="%s"
         android:title="@string/settings_recording_track_name_title" />
     <de.dennisguse.opentracks.settings.ActivityTypePreference
         android:defaultValue="@string/activity_type_running"
         android:key="@string/default_activity_key"
+        android:summary="%s"
         android:title="@string/settings_recording_default_activity_title" />
     <ListPreference
         android:defaultValue="0"
         android:key="@string/min_recording_interval_key"
+        android:summary="%s"
         android:title="@string/settings_recording_min_recording_interval_title" />
     <ListPreference
         android:defaultValue="10"
         android:key="@string/recording_distance_interval_key"
+        android:summary="%s"
         android:title="@string/settings_recording_min_recording_distance_title" />
     <ListPreference
         android:defaultValue="200"
         android:key="@string/max_recording_distance_key"
+        android:summary="%s"
         android:title="@string/settings_recording_max_recording_distance_title" />
     <ListPreference
         android:defaultValue="50"
         android:key="@string/recording_gps_accuracy_key"
+        android:summary="%s"
         android:title="@string/settings_recording_min_required_accuracy_title" />
     <ListPreference
         android:defaultValue="10"
         android:key="@string/auto_resume_track_timeout_key"
+        android:summary="%s"
         android:title="@string/settings_recording_auto_resume_track_timeout_title" />
 </PreferenceScreen>

src/main/res/xml/settings_sensors.xml

@@ -27,6 +27,7 @@ limitations under the License.
         <ListPreference
             android:defaultValue="@string/sensor_type_value_none"
             android:key="@string/bluetooth_sensor_key"
+            android:summary="%s"
             android:title="@string/settings_sensor_bluetooth_sensor" />
     </PreferenceCategory>
 </PreferenceScreen>

src/main/res/xml/settings_statistics.xml

@@ -18,10 +18,12 @@ limitations under the License.
     <ListPreference
         android:defaultValue="@string/stats_units_metric"
         android:key="@string/stats_units_key"
+        android:summary="%s"
         android:title="@string/settings_stats_units_title" />
     <ListPreference
         android:defaultValue="@string/stats_rate_speed"
         android:key="@string/stats_rate_key"
+        android:summary="%s"
         android:title="@string/settings_stats_rate_title" />
     <PreferenceCategory android:title="@string/settings_show">
         <CheckBoxPreference