Add configurable buttons, separate settings screens and backup activity

- Add ButtonConfigActivity for customizing main screen buttons with
  drag-and-drop reordering and individual size options (S/M/L)
- Move storage settings to separate StorageSettingsActivity
- Move signature setting to storage settings (relevant for WebDAV sync)
- Move data backup to separate BackupActivity with export/import
- Make "more" overflow button configurable in size
- Simplify SettingsActivity to 3 navigation buttons
- Add logbook rename/delete functionality
- Improve S/M/L button contrast with visible borders

app/src/main/AndroidManifest.xml

@@ -34,6 +34,18 @@
             android:name=".StatisticsActivity"
             android:label="@string/statistics_title"
             android:theme="@style/Theme.LunaTracker"/>
+        <activity
+            android:name=".ButtonConfigActivity"
+            android:label="@string/button_config_title"
+            android:theme="@style/Theme.LunaTracker"/>
+        <activity
+            android:name=".StorageSettingsActivity"
+            android:label="@string/storage_settings_title"
+            android:theme="@style/Theme.LunaTracker"/>
+        <activity
+            android:name=".BackupActivity"
+            android:label="@string/backup_title"
+            android:theme="@style/Theme.LunaTracker"/>
     </application>
 
 </manifest>