Support multiple background-processing utilities

[acozine]

We currently support resque. Consider adding alternatives:

• [ ] sidekiq
• [ ] delayed_job
• [ ] rabbitmq

[acozine]

Changes to use sidekiq are mainly in the codebase rather than in the server setup:

• add gem 'sidekiq' and gem 'capistrano-sidekiq' to the Gemfile
• add require "capistrano/sidekiq" in the Capfile
• set config.active_job.queue_adapter = :sidekiq in config/environments/production.rb
• create config/initializers/sidekiq.rb to connect sidekiq to redis
• create config/sidekiq.yml to define the queues, and match the setting of the ingest queue in config/initializers/hyrax.rb - e.g. config.ingest_queue_name = :ingest
• if desired, add require 'sidekiq/web' and mount Sidekiq::Web => '/sidekiq' to config/routes.rb to add the sidekiq management pane

See https://github.com/curationexperts/nurax/commit/a93f77c8a77702e5fb68c6453c5d870001537451 for some of the changes described above.

[mark-dce]

Standardizing on community preferred use of sidekiq in https://github.com/curationexperts/ansible-samvera