feature #221:
Ajout d'une classe pour verifier la connection.
On verifie si on a le net au moment d'appuyer sur login.
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@+id/contact_list_menu_add_contact"
android:visible="true"
android:title="@string/contact_list_menu_add_contact"
android:icon="@drawable/ic_menu_add" />
<item android:id="@+id/contact_list_menu_settings"
android:visible="true"
android:title="@string/contact_list_menu_settings"
android:icon="@drawable/ic_menu_manage" />
</menu>