enable the Action/Toolbar for Settings screens

by using a theme that has it enabled

Change-Id: Icf3b66d38de55e2b08d4e4ced463bab045e56c43

android/source/AndroidManifest.xml

@@ -95,6 +95,7 @@
 
         <activity
             android:name=".SettingsActivity"
+            android:theme="@style/Theme.AppCompat.Light.DarkActionBar"
             android:label="@string/app_name_settings">
         </activity>
 
@@ -109,6 +110,7 @@
 
         <!-- Document Provider Settings Activity -->
         <activity android:name=".storage.DocumentProviderSettingsActivity"
+                  android:theme="@style/Theme.AppCompat.Light.DarkActionBar"
                   android:label="@string/storage_provider_settings">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

android/source/src/java/org/libreoffice/storage/DocumentProviderSettingsActivity.java

@@ -14,7 +14,6 @@ import java.util.Set;
 import org.libreoffice.R;
 import org.libreoffice.storage.external.BrowserSelectorActivity;
 
-import android.app.Activity;
 import android.content.Intent;
 import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
 import android.os.Bundle;
@@ -22,8 +21,9 @@ import android.preference.Preference;
 import android.preference.PreferenceFragment;
 import android.preference.PreferenceManager;
 import android.preference.PreferenceScreen;
+import android.support.v7.app.AppCompatActivity;
 
-public class DocumentProviderSettingsActivity extends Activity {
+public class DocumentProviderSettingsActivity extends AppCompatActivity {
 
     public static final String KEY_PREF_OWNCLOUD_SERVER = "pref_server_url";
     public static final String KEY_PREF_OWNCLOUD_USER_NAME = "pref_user_name";