android: Show document browser back in the menu

Related with commit c7c2b4b5.

There is nothing wrong with having several activities; in fact Android
development encourages using one activity per use case. After this
patch we have:

* One menu item that opens LibreOffice document browser. It covers the
  use case "open LibreOffice without documents".
* The viewer activity does not have a menu item but it responds to
  open intents triggered by any applications like file explorers,
  including the document browser.

Change-Id: Ie08b96e52d3a6a79aed3354620302705d7689381
Reviewed-on: https://gerrit.libreoffice.org/12108Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>

android/experimental/LOAndroid3/AndroidManifest.xml.in

@@ -17,14 +17,11 @@
         android:label="@string/app_name"
         android:hardwareAccelerated="true"
         android:theme="@style/AppTheme">
+        <!-- Viewer Activity -->
         <activity
             android:name="org.libreoffice.LibreOfficeMainActivity"
             android:label="@string/app_name"
             android:configChanges="orientation|keyboard|keyboardHidden|screenLayout|uiMode|screenSize|smallestScreenSize">
-            <intent-filter>
-                <action android:name="android.intent.action.MAIN" />
-                <category android:name="android.intent.category.LAUNCHER" />
-            </intent-filter>
             <intent-filter>
                 <action android:name="android.intent.action.VIEW" />
                 <action android:name="android.intent.action.EDIT" />
@@ -84,17 +81,14 @@
             </intent-filter>
         </activity>
         <!-- Document Browser Activity -->
-        <!-- Disable it here so that we don't present two icons.
-             TODO Probably merge the two activities, so that the browser opens when LibreOffice is started with no document.
         <activity android:name=".ui.LibreOfficeUIActivity"
-                  android:label="@string/browser_app_name"
+                  android:label="@string/app_name"
                   android:theme="@android:style/Theme.Holo">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
-        -->
     </application>
 
 </manifest>