rework EnumType to use better Enum's

unfortunately IntEnum can't be bent like we would need it (extensible).
So we had to write our own....

The members of the Enum still behave like ints, but also have
.name and .value attributes, should they be needed.

needed adoptions to correctly use (and test) the EnumType are included.

Change-Id: Ie019d2f449a244c4fab00554b6c6daaac8948b59
Reviewed-on: https://forge.frm2.tum.de/review/17843
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>

secop/lib/__init__.py

@@ -49,6 +49,8 @@ CONFIG = {
 }
 
 
+unset_value = object()
+
 class lazy_property(object):
     """A property that calculates its value only once."""