Update JNA to 4.1.0.

JNA 4.1.0 has a proper license, so remove workaround in
licenseCompleter.groovy. [JENKINS-24521]
Update libpam4j to 1.8, which uses JNA 4.0
Update memory-monitor to 1.9 which uses JNA 4.1
Accept "field" specified in the surrounding <f:entry> since this one expects <f:entry>
[FIXED JENKINS-3539] Prevent empty file creation if left empty
Merge branch 'master' of https://github.com/jenkinsci/jenkins into JENKINS-3539

Conflicts:
	test/src/test/java/hudson/model/ParametersTest.java
Merge pull request #1428 from daniel-beck/JENKINS-3539

[FIXED JENKINS-3539] Prevent empty file creation if left empty
Noting #1428

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Improve #1428 note

The commit message cannot really stand alone.
Documenting what this setting controls
Restored backward compatibility.

Up to b5843f3, <t:ballColorTd> supported @iconSize="16x16" and so on that controls the color.
In the new scheme, it needs to be translated to iconSizeClass
[FIXED JENKINS-24521] Merge branch 'pull-1387'