CodingGuideline.rst: add Form Best practice

Documentation/CodingGuideline.rst

@@ -77,3 +77,11 @@ QFQ content record
       }
 
 * Always comment the queries like shown above.
+
+QFQ Form
+--------
+
+* Mandatory SIP parameter have to be mentioned in Form.requiredNew and/or Form.requiredEdit.
+* If the title of a FormElement isn't descriptive enough, use tooltip, note or extraButtonInfo to explain to a user.
+* Every Form should show a descriptive title to identify the task and current record. E.g. Not 'Person' but 'Person: John Doe'.
+* Often the length of a pill title if not sufficient, use a tooltip to give a more descriptive hint.