Fixes #19585 - Allow csv export of nested attributes

This is required for example to export host facet attributes.

Fixes #18760 - Allow export to CSV

This introduces a way of exporting tables from the UI to CSV.
There are 3 steps to adding a CSV export to a table:

1. Add the CsvResponder concern to the relevant controller.
2. Add a `format.csv` block to the index controller action. This block...

fixes #18665 - call #to_h before comparing AC::Parameters to hash

Allows comparisons when ActionController::Parameters is separated from
Hash in Rails 5.0. #permit! is now called on inner hashes sent through
KeepParam (similar to rails/rails@e86524c in 5.1) so they are included...

fixes #17300 - accept Nic::Bond#attached_devices string inputs

fixes #16557 - move tests into modern Rails layout

Models, controllers, mailers and helpers are now in test/ subdirs
matching app/ subdirs. Service, miscellaneous and old test/lib/ tests
are now in test/unit/ separated from models, which obsoletes the custom...