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/properties.py

@@ -48,7 +48,7 @@ class Property(object):
         self.description = description
         self.default = datatype.default if default is None else datatype(default)
         self.datatype = datatype
-        self.extname = unicode(extname)
+        self.extname = extname
         self.export = export or bool(extname)
         self.mandatory = mandatory or (default is None and not isinstance(datatype, ValueType))
         self.settable = settable or mandatory  # settable means settable from the cfg file
@@ -121,8 +121,9 @@ class PropertyMeta(type):
 class HasProperties(object):
     properties = {}
 
-    def __init__(self, *args):
-        super(HasProperties, self).__init__()
+    def __init__(self, supercall_init=True):
+        if supercall_init:
+            super(HasProperties, self).__init__()
         # store property values in the instance, keep descriptors on the class
         self.properties = {}
         # pre-init with properties default value (if any)