fixes #13618 - cache expensive vmware api calls

Refs #15779 - make background processing unavailable for now (#4217)

The original PR got vetted in the packaging phase and including
foreman-task as dependency of Foreman was refused. We need to rethink
our approach for getting the foreman-tasks functionality available...

Fixes #17681 - Switch to newly created taxonomy

Refs #17653 - fix typo in show_hidden_parameters and add tests

Refs #17653 - add show_hidden to apidoc

fixes #17545 - adds UI notification support

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

Fixes #18045 - Puppet classes show up choosing only env.

After #3551 was merged, the hosts controller requires both environment
and hostgroup to be set in order to display puppetclasses.

It shouldn't be required to have both, so we should check what's
available and use it. If it's only the hostgroup or the environment, it...

Fixes #6502 - List ignored classes and environments on import

When importing environments and classes from puppet, ignored
environments and classes defined in ignored_environments.yml
aren't aparent.

This will add them to the list to import as ignored and...

Fixes #15403 - moved puppet to a concern in hosts UI controller

Fixes #17015 - Adds Key pairs controller