Lots of code cleanup and improvements after inspection

Load Today tasks in a AsyncTask
Use of plurals instead of string
Menu icons change
No more tasks now displayed in the center of the screen

DoNExt/app/src/main/res/values-fr/arrays.xml

@@ -4,8 +4,4 @@
         <item>Simple</item>
         <item>Détaillée</item>
     </string-array>
-    <string-array name="settings_today_actions">
-        <item>Terminer</item>
-        <item>Réinitialiser</item>
-    </string-array>
 </resources>