fixes #18214 - accept `params` as AC::Parameters or Hash

In Rails 5, ActionController::Parameters no longer inherits from Hash
and so type checks for params.is_a?(Hash) now return false and should
accept either. (Rails commit 14a3bd5.)

fixes #17545 - adds UI notification support

- Initial data model for notification support, based on manageiq design.
- addes notification JSON endpoints.

Fixes #16740 - Access host params through macro

Fixes #17874 - Extract contains_erb? from lookup key

Fixes #17015 - Adds Key pairs controller

fixes #16459 - remove 1.15 deprecations

Fixes #16739 - unify parameters permissions

Fixes #17403 - enable exporting of templates

Fixes #14688 - Power status visible on hosts index page

Fixes #17309 - Made facets resilient to class reloading

Now the configuration is stored in plugin declaration.
If you are using `Facets.register` directly, please make sure
you are re-registering it after reload occurs.