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/protocol/interface/tcp.py

@@ -211,7 +211,7 @@ class TCPServer(HasProperties, socketserver.ThreadingTCPServer):
         self.dispatcher = srv.dispatcher
         self.name = name
         self.log = logger
-        super(TCPServer, self).__init__()
+        HasProperties.__init__(self, supercall_init=False)
         bindto = options.pop('bindto', 'localhost')
         bindport = int(options.pop('bindport', DEF_PORT))
         detailed_errors = options.pop('detailed_errors', False)