6545 add generic navbar

Route: Don't run `#calculate_costs!` during a referential merge. Fixes #6410

This callback got triggered during a referential merge, but it isn't
needed at that point. It should only be executed as a result of a user
updating the route (via the web interface).

Using Alban's suggestion, we can detect that we're in the process of a
merge if the associated referential is in a `ReferentialSuite`. Use this
as a condition to run the callback.

Refs #6410

Update acts_as_list. Refs #6179 

And (hopefully) fix bugs on routes having duplicated positions

Use an `after_commit` instead of an `after_save`. The `after_save` could
cause intermittent problems due to Sidekiq starting before the
record/transaction actually gets committed to the database. In those
cases, the record wouldn't be found and cause an error.

With an `after_commit` callback, the record is sure to be committed
before Sidekiq takes over.

Additionally, limit the callback to `:create` and `:update` because
otherwise it will be active on `:destroy` by default also. This work
isn't relevant on destroy, so don't do it then.

Update the tests:

* Update labels
* Use `build` instead of `create` because we're saving the record at the
  end anyway so we don't need an object that starts out persisted
* Use `truncation: true` for these tests because otherwise the `commit`
  callback doesn't get called due to transactional teardown

Refs #6407