Viur-datastore

Added
- Re-added startDataAccessLog and endDataAccessLog functions

Changed
- Replaced Beta classifier with Production/Stable

Added
- unit-test for in-filter on \_\_keys\_\_

Fixed
- Fixed handling of incomplete/null keys

Changed
- Moved config variables from query.py to separate config file

Fixed
- traceQueries now logs all queries

Removed
- Implicit import from viur-core.config.SkeletonInstanceRef has now to be set from outside.

Fixed
- Missing imports & typos in query.py
- Compiler and build warnings

Added
- Export AllocateIDs by default (needed for the new import system in viur-core)

Fixed
- Passing an empty list to delete() raising an exception
- Deprecation warnings regarding simdjson::element:at