Feature: sort and select scenarios in main scenario selection drop-down

[victorterpstra]

For demo purposes, allow a user to select a subset of scenarios to be included in the main scenario-select drop-down. I.e. hide scenarios that are not relevant at this moment. Also, allow a user to define a custom sort-order of the scenario. This supports telling a 'story' where we run through a sequence of scenarios. Allowing a sort-order avoids the need to name scenarios alphabetically.

Technically:

• Add a 'hide' Boolean column to the Scenario table. Allow a user to toggle the hide property
• Add a 'sort_order` integer column to the Scenario table. Default = 0. Allow user to edit.
• Show scenarios in drop-down:
  • not hidden
  • sort first by sort_order, second by name

[victorterpstra]

• Add a display_name column to customize the name of the scenario in the drop-down (if feasible?)