[ADD] point_of_sale: How to handle split bills?

https://docs.google.com/document/d/1W97iepD0J5zIdJEymEGqORoIEw-xUMMMNnvV4Kl0WCg/edit

point_of_sale/restaurant/split.rst

@@ -1,3 +1,84 @@
 ==========================
 How to handle split bills?
-==========================
+==========================
+
+Configuration
+=============
+
+Split bills only work for point of sales that are in **restaurant** mode.
+
+From the dashboard click on :menuselection:`More --> Settings`:
+
+.. image:: media/split01.png
+    :align: center
+
+In the settings tick the option **Bill Splitting**.
+
+.. image:: media/split02.png
+    :align: center
+
+Register an order
+=================
+
+From the dashboard, click on **New Session**.
+
+.. image:: media/split03.png
+    :align: center
+
+Choose a table and start registering an order.
+
+.. image:: media/split04.png
+    :align: center
+
+When customers want to pay and split the bill, there are two ways to
+achieve this:
+
+-  based on the total
+
+-  based on products
+
+.. image:: media/split05.png
+    :align: center
+
+Splitting based on the total
+----------------------------
+
+Just click on **Payment**. You only have to insert the money tendered by
+each customer.
+
+Click on the payment method (cash, credit card,...) and enter the
+amount. Repeat it for each customer.
+
+.. image:: media/split06.png
+    :align: center
+
+When it's done, click on validate. This is how to split the bill based
+on the total amount.
+
+Split the bill based on products
+--------------------------------
+
+On the main view, click on **Split**
+
+.. image:: media/split07.png
+    :align: center
+
+Select the products the first customer wants to pay and click on **Payment**
+
+.. image:: media/split08.png
+    :align: center
+
+You get the total, process the payment and click on **Validate**
+
+.. image:: media/split09.png
+    :align: center
+
+Follow the same procedure for the next customer of the same table.
+
+When all the products have been paid you go back to the table map.
+
+.. seealso::
+    * :doc:`../shop/cash_control`
+    * :doc:`../shop/invoice`
+    * :doc:`../shop/refund`
+    * :doc:`../shop/seasonal_discount`