Settings: scan for Bluetooth sensors rather than using bonded devices.

Bonded devices do no provide information what services (e.g., heart rate) they support.

src/main/res/values/strings.xml

@@ -1055,7 +1055,13 @@ limitations under the License.
     Sending
   </string>
   <string name="sensor_not_known" translation_description="Error message if sensor is not available in Android (e.g., pairing was removed in Bluetooth Settings).">
-    Sensor %1$s is not known. Please check the settings.
+    Sensor %1$s is unknown. Please check the settings.
+  </string>
+    <string name="sensor_could_not_scan">
+    Could not scan for Bluetooth devices (error %1$i).
+  </string>
+  <string name="bluetooth_disabled">
+    Please enable Bluetooth.
   </string>
     <!-- Settings -->
     <string name="settings_not_while_recording" translation_description="In settings, the summary for an option that is not available during a
@@ -1220,7 +1226,7 @@ limitations under the License.
   </string>
 
   <string name="settings_error_initial_values_restored" translation_description="If the ">
-    Sorry, but an error occurred: and the all settings were reset to there default values.
+    Sorry, but an error occurred. All settings have been reverted to the default values.
   </string>
 
   <!-- Settings Sensor -->

src/main/res/xml/settings.xml

@@ -130,11 +130,10 @@ limitations under the License.
     </PreferenceCategory>
 
     <PreferenceCategory android:title="@string/settings_sensor">
-        <ListPreference
+        <de.dennisguse.opentracks.settings.BluetoothLeListPreference
             android:defaultValue="@string/sensor_type_value_none"
             android:key="@string/settings_sensor_bluetooth_sensor_key"
-            android:title="@string/settings_sensor_bluetooth_sensor"
-            app:useSimpleSummaryProvider="true" />
+            android:title="@string/settings_sensor_bluetooth_sensor" />
         <Preference
             android:key="@string/settings_sensor_bluetooth_pairing_key"
             android:persistent="false"