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

@@ -23,7 +23,7 @@ ForwardMap = Dict[ExternalFlag, float]
 BackwardMap = Dict[float, ExternalFlag]
 
 
-class TranslationScheme:
+class TranslationScheme:  # pragma: no cover
     @property
     @abstractmethod
     def DFILTER_DEFAULT(self):