Track recording service handles the status of recording: track's id, pause and GPS status.

Created an interface for all components that want to know about recording status through the service.
All interface's methods are optional so every component can implement what they need.
Fixes #388.

src/main/res/values/preferences_internal.xml

@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?><!--
-Copyright 2010 Google Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-     http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
--->
-<resources>
-    <!-- Keys for persisted preferences that are used by internally. -->
-    <!--But they should not get backed up or restored.-->
-    <string name="recording_track_id_key" translatable="false">recordingTrackId</string>
-
-    <string name="recording_track_paused_key" translatable="false">recordingTrackPaused</string>
-    <bool name="recording_track_paused_default" translatable="false">true</bool>
-</resources>

src/main/res/values/settings.xml

@@ -31,6 +31,9 @@
     <string name="post_workout_export_enabled_key" translatable="false">instantExportEnabled</string>
     <bool name="post_workout_export_enabled_default" translatable="false">false</bool>
 
+    <string name="settings_import" translatable="false">settingsImport</string>
+    <string name="settings_export" translatable="false">settingsExport</string>
+
     <string name="default_activity_key" translatable="false">defaultActivity</string>
     <string name="default_activity_default" translatable="false">@string/activity_type_unknown</string>
     <string-array name="activity_types">