[FIXED JENKINS-31649] Check should be against AccessControlled not Item

- The previous check was to narrow.
- We now check on AccessControlled (which is implemented by Item)
- We now also check on Permission.READ (which is the generic read permission)

This should allow subtasks who's task may not be an Item to at least implement AccessControlled to alow visibility.

There remains an open question as to whether tasks that are not AccessControlled should ever be visible in the UI

[Fixed JENKINS-31631] Handle YUI submit <button> clicks

[FIXED JENKINS-31596] Provide an extension point for MasterKillSwitchConfiguration relevance

Improve de translation of loginLink

Should be uppercase to be consistent with the sign up link

- The MasterKillSwitchConfiguration was not available when you have clouds but no fixed slaves.
- The MasterKillSwitchConfiguration was not available when it was enabled but for a non-relevant configuration.

[JENKINS-27505] Preserve an empty line at the beginning of a textarea

[FIXED JENKINS-31235] fix createItem/copy API args

Enhance SimpleBuildStep readability for workflow

[FIX JENKINS-31015] Prevent InvalidPathException in FileVF

Intentionally leaving out post 1.637 changes in preparation of the
security 1.638 release roll out.

[SECURITY-218] - Functional tests for CLI

[SECURITY-218] Blackbox test

remove unused import statements

In addition to cluttering the namespace, unused imports generate
compiler warnings, introducing noise and obscuring more important
compiler warnings.  This change removes them.