Add more docs for Feature Layer

not complete, but progress..

docs/features/purchasing/ordering/execution.rst

@@ -0,0 +1,22 @@
+
+Batch Execution
+===============
+
+Often the user will have made an Ordering batch and added items to it
+"manually" when assembling their order.
+
+But in some cases the PO data will have been imported from some other
+system, or perhaps a CSV file, with the goal being just to get it into
+the POS system.
+
+Regardless of how the batch data was obtained (e.g. from file, or user
+input), ultimately the batch will be executed.  So what does that do?
+
+This basically depends on what you need it to do...  For instance in
+the CSV file example just mentioned, if your goal is merely to get the
+PO data into the POS system, then that's what executing the batch
+should do.
+
+It is possible also to make batch execution actually "submit"
+(e.g. email) the purchase order to the vendor, although this is less
+common in practice.