Translation cleanups

A number of cleanups and disentanglements to the current translator implementations:

• Extract a real abstract Translator interface
• Remove the mapping based approach from the FloatTranslator to make it actually accept floating point values unequal exact integers

saqc/core/translation/basescheme.py

@@ -24,7 +24,8 @@ BackwardMap = Dict[float, ExternalFlag]
 
 
 class TranslationScheme:
-    @abstractproperty
+    @property
+    @abstractmethod
     def DFILTER_DEFAULT(self):
         pass