import cleanups

• moved saqc.core.register._isflagged to saqc.lib.tool.isflagged
• moved saqc.core.{reader, visitor} to saqc.parsing.{reader, visitor}
• added saqc.core.frame module that acts as a bridge to out data-collection-class (currently dios.DictOfSeries)
• removed all direct imports of dios
• cleand up imports (always import from the highest possible level)
• moved SimpleScheme from saqc.core.basescheme.py to new file saqc.core.translation.simplescheme.py
• cleaned constants.py to only hold real constants

i removed all direct references to dios, to simplify maintenance of out dataclass and in preparation of the new data container

saqc/core/__init__.py

 #! /usr/bin/env python
-
 # SPDX-FileCopyrightText: 2021 Helmholtz-Zentrum für Umweltforschung GmbH - UFZ
-#
 # SPDX-License-Identifier: GPL-3.0-or-later
-
 # -*- coding: utf-8 -*-
 
 # isort: skip_file
@@ -11,6 +8,4 @@ from saqc.core.frame import DictOfSeries, to_dios  # noqa
 from saqc.core.history import History
 from saqc.core.flags import Flags, initFlagsLike
 from saqc.core.register import flagging, processing, register
-
-# from saqc.core.translation import DmpScheme, FloatScheme, PositionalScheme, SimpleScheme
 from saqc.core.core import SaQC