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

tests/core/test_translator.py

@@ -16,7 +16,7 @@ import pytest
 from saqc.constants import BAD, DOUBTFUL, FILTER_NONE, UNFLAGGED
 from saqc.core.core import SaQC
 from saqc.core.flags import Flags
-from saqc.core.translation import DmpScheme, PositionalScheme, MappingScheme
+from saqc.core.translation import DmpScheme, MappingScheme, PositionalScheme
 from tests.common import initData