fixup! wendelin.core: Add way to run tests

In 805374b4 I established the way to run wendelin.core test.  There
component/wendelin.core/test-common.cfg preamble mimics what is setup
by software/neoppod/software-common.cfg in parts for NEO. However I
copied only neoppod into parts without neoppod-develop, and this results
in NEO being installed from PyPI instead of from git checkout.

Let's fix this because everything else - e.g. ERP5 and Wendelin software
releases - use NEO from git checkout which today diverged significantly
from what was last released to PyPI in April of 2019.

Thanks to @jerome for helping to find this out.

component/wendelin.core/test-common.cfg

@@ -14,6 +14,7 @@ extends =
 
 parts =
 # keep neoppod first and in parts so that ZODB is built correctly
+    neoppod-develop
     neoppod
 
 #   for instance