fix some remaining py3 incompatibilites

- None <= 0  is invalid in py3
- restrict BLOBType to bytes (may be changed after migration to py3)
- remove long
- use list(<dict>.items()) when dict is changed within loop
- allow initialization of properties in HasProperties without
  supercall to base class
- <dict>.values() can not be indexed
- adapted/removed various tests. additional tests might be added
  after definitive migration to py3

after this change, all the tests run with py3, also secop-server and
secop-gui were tested with an example, but other code might still contain
py3 incompatibilities

Change-Id: I881c6972aeabb8494a21a6cbc7ffeddfd4f5d4f8
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/21306
Tested-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
Reviewed-by: Bjoern Pedersen <bjoern.pedersen@frm2.tum.de>

secop/modules.py

@@ -192,7 +192,7 @@ class Module(HasProperties):
 
         # 5) 'apply' config:
         #    pass values through the datatypes and store as attributes
-        for k, v in cfgdict.items():
+        for k, v in list(cfgdict.items()):
             # apply datatype, complain if type does not fit
             datatype = self.parameters[k].datatype
             try: