Improve tabs UX and saving/loading

- Show icons in the tabs list and dialog chooser
- Add a "restore to defaults" button
- Make removing gesture more user intuitive

app/src/main/res/values/attrs.xml

@@ -36,6 +36,8 @@
     <attr name="ic_save" format="reference"/>
     <attr name="ic_backup" format="reference"/>
     <attr name="ic_add" format="reference"/>
+    <attr name="ic_restore_defaults" format="reference"/>
+    <attr name="ic_blank_page" format="reference"/>
 
     <!-- Can't refer to colors directly in drawable's xml-->
     <attr name="toolbar_shadow_drawable" format="reference"/>