Split DataSelector into a generic component and an ORNL-specific one (#112)
* Clean up the pyproject.toml file and document changes * Move existing DataSelector to NeutronDataSelector * Split gallery tests for DataSelector classes * Inherit the DataSelector model properly * Inherit the DataSelector view and vm properly * Remove skip_init parameter * Fix doc builds and give a useful error message if one imports the old DataSelector class * Fix treeview indentation CSS