introduced Datatype.copy

as Datatype got mutable, it has to be copied when inherited.
Params.copy must call the introduced method Datatype.copy.

in addition:
- fixed bugs in ScaledInteger.__repr__ and datatypes.DATATYPES['struct']
- do not export unit from Parameters

Change-Id: Id552c33843b1b2bedffc68d1bd909705dcfb5605
Reviewed-on: https://forge.frm2.tum.de/review/20324
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/params.py

@@ -44,7 +44,7 @@ class Accessible(CountedObj):
             ['%s=%r' % (k, v) for k, v in sorted(self.__dict__.items())]))
 
     def copy(self):
-        # return a copy of ourselfs
+        '''return a copy of ourselfs'''
         props = self.__dict__.copy()
         return type(self)(**props)
 
@@ -146,11 +146,15 @@ class Parameter(Accessible):
         if ctr is not None:
             self.ctr = ctr
 
+    def copy(self):
+        '''return a copy of ourselfs'''
+        result = Accessible.copy(self)
+        result.datatype = result.datatype.copy()
+        return result
+
     def for_export(self):
         # used for serialisation only
         res = self.exported_properties()
-        if self.unit:
-            res['unit'] = self.unit
         return res
 
     def export_value(self):