edited property needs datatype

https://gitlab.indiscale.com/caosdb/internal/all/-/issues/141

src/doc/tutorials/Data-Insertion.rst

@@ -10,7 +10,8 @@ at the chapter :any:`caosdb-server:Data Model` .
 
 In order to insert some actual data, we need to create a data model
 using RecordTypes and Properties (You may skip this if you use a CaosDB
-instance that already has the required types). So, let’s create a simple
+instance that already has the required types). When you create a new Property 
+you must supply a datatype. So, let’s create a simple
 Property called “a” of datatype double. This is very easy in pylib:
 
 .. code:: python