Fixes #19534 - improved orchestration task logging

fixes #19464 - rewrite Dashboard::Manager to support autoloading

Replaces class-level widget storage with a static list of built-in
widgets, then appends the registered plugin widgets to get the full
default list of widgets. As a result, the class can safely be reloaded...

fixes #19317, #10927 - move registries to autoload_once path

Partially reverts 70ce8fe to reinstate autoload_once_paths as the
preferred way to load registry-type objects with class variables
containing data set up during app initialisation (e.g. plugin
registrations, menu items.)...

fixes #19192 - adds mark all as read notification action

This implements missing feature from patternfly ( see http://www.patternfly.org/pattern-library/communication/notification-drawer/#/code/angular)

fixes #18445 - always define eager_load_paths, use require_dep

Allows `eager_load!` to be called or enabled in any environment without
loading files under lib/ twice. Switches many `require` calls to Rails'
`require_dependency` to always use its dependency loader, so when eager...

Fixes #18561 - faster fact deletion on MySQL

Fixes #18954 - Add CSV export to facts table

Fixes #18957,#18193,#18678,#18853 - notifications redux

Refactored notifications to work with redux, fixed
several UI related bugs, added tests.
flux is now unused, this is based on @gailsteiger's
previous work.

fixes #19035 - rewrite TopbarSweeper without rails-observers

Moves from the observer object into two mixins, one on the model and one
on the top-level controllers to observe creates/updates/destroys on
monitored models. Replaces rails-observers as it lacks Rails 5 support.

fixes #18940 - adds caching to notification api calls.

this implementation reduce the notification fetching time on
my production system from avg response times of 80ms to 20ms,
and siginficantly reducing server load (db, cpu etc)

it also removes total counts from the implementation, as that was not...