moved mocked unit to fake epics, added pv name to repr of PV wrapper

slic/utils/pv.py

@@ -3,12 +3,11 @@ import epics
 
 class PV(epics.PV):
 
-    units = b"km"
-
     def __repr__(self):
+        name = self.pvname
         val = self.get()
         units = self.units.decode()
-        return "PV at {} {}".format(val, units)
+        return "PV \"{}\" at {} {}".format(name, val, units)