Fixes #19612 - CVE-2017-7505 don't expose admin to taxed users

Fixes #19632 - changed shim and grub1 PXE names

Fixes #16159 - Rename mail alerts to not be Puppet specific

Right now, under 'my account', users get emails with alerts about the
status of their hosts regarding configuration management (e.g: if there
was an error, get an alert, or get a weekly summary of all hosts...

fixes #18200 - don't re-encrypt settings when value is unchanged

Fixes #19034 - add tasks for clearing expired notifications

fixes #19528 - rewrite FiltersHelperOverrides to support autoload

Replaces class-level filter search overrides storage with a query
against Foreman::Plugin, allowing the class to be reloaded and tested
safely. Removes another 'registry' class.

Fixes #19630 - ignore hidden admins

Fixes #19583 - reworded blank label for subnet

Fixes #19475 - Rename test variables to more specific term

An issue occurring with a recent minitest upgrade broke tests.
Renaming variables set with let to a less ambiguous wording is
to work around the issue.

refs #19534 - check EncryptValue class variables are defined

bed4594 added class variables to record logging state, but failed to
check it was defined before accessing them, causing exceptions when
decryption failed. Tests added for this new behaviour.