BaseYear being duplicated into multiple scenarios on export #20
Description
The new export machinery (VE 3.0.3) dumps the full Datastore for each scenario.
It works to set up scenarios with the "no build" FutureYear set to StartFrom the BaseYear, and then use BaseScenario so the subsequent scenarios will run with the "no build" FutureYear inputs conditionally replaced.
However, when we export those scenarios, the full Datastore is included for each Scenario, including the BaseYear. So for exporting, we need to filter the Datastore so the only groups it should include are ones defined in the Years configuration for the Stage/Scenario. The BaseYear should be Reportable, and it will be exported because its "Years" match "BaseYear".
We can implement that with a default selection that sets the Groups to just the Years defined in the Scenario configuration. That should happen at a very low level when we identify the groups to be generated for the scenario.
Can we also skip doing the "Global" group for any scenario other than the BaseYear? We'll need to review what exactly gets pushed into Global (things like geo.csv for sure, which don't need to be reproduced necessarily). Some flag or configuration to request that Global be generated (or not) in a particular scenario)...