issues with StructOf

- depending whether client or server side, handling of optional is different
- fix issues when struct is used as keyworded command arguments

Change-Id: I72b347b1a96ee3bce1f67dace4862c313c12c7a9
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/30972
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

cfg/test_cfg.py

@@ -1,7 +1,7 @@
 Node('test.config.frappy.demo',
      '''short description of the testing sec-node
 
-This description for the Nodecan be as long as you need if you use a multiline string.
+This description for the node can be as long as you need if you use a multiline string.
 
 Very long!
 The needed fields are Equipment id (1st argument), description (this)
@@ -51,3 +51,8 @@ Mod('Decision',
     'that can be converted to a list',
     choices = ['Yes', 'Maybe', 'No'],
 )
+
+Mod('c',
+    'frappy_demo.test.Commands',
+    'a command test',
+)