WIP: overhaul lookup table classes and structure
- moves the definition of LookupTable to rtctools._internal.lookup_table
- defines CSVLookupTableProvider class in rtctools._internal.csv_lookup_table_provider
- rtctools.optimization.CSVLookupTableMixin inherits from CSVLookupTableProvider
- new rtctools.simulation.CSVLookupTableMixin inherits from CSVLookupTableProvider
- update documentation with new rtctools.simulation.CSVLookupTableMixin
Edited by Teresa Piovesan