Add message details menu button

Adds a "Properties" menu button in conversation, when one message
is selected, which displays details about the message:
- Type (SMS or MMS)
- Sender phone number (or receiver if it is a sent message)
- Used SIM
- Date sent at
- Date received at (if it is an incoming message)

This closes #19

app/src/main/res/menu/cab_thread.xml

@@ -26,6 +26,11 @@
         android:icon="@drawable/ic_save_vector"
         android:title="@string/save_as"
         app:showAsAction="ifRoom" />
+    <item
+        android:id="@+id/cab_properties"
+        android:icon="@drawable/ic_info_vector"
+        android:title="@string/properties"
+        app:showAsAction="ifRoom" />
     <item
         android:id="@+id/cab_forward_message"
         android:showAsAction="never"