FEATURE: Add custom dashboards without overwriting default dashboards

[dougburks]

As a defender, I'd like to be able to add custom dashboards without overwriting default dashboards. Currently, if I go to SOC Config and add a new dashboard, then whenever I run soup I'm stuck with my same list of dashboards instead of being able to take advantage of any new dashboards that were added in the update. The current functionality is good for users that may want to remove one or more dashboards from our default list and never see them again and we should continue to support that as a feature. It would be nice to have a separate method for adding a custom dashboard that doesn't impact the default dashboards.