Update the detached version of Maven plugin to 2.14

We have to do it, because some extension points are being executed on slaves (e.g. https://github.com/jenkinsci/cygwin-process-killer-plugin/blob/master/src/main/java/com/synopsys/arc/jenkinsci/plugins/cygwinprocesskiller/CygwinProcessKiller.java - ProcessKiller EP gets propagated).

It's a follow-up to https://github.com/jenkinsci/jenkins/pull/2568

[JENKINS-39363,CID-1205051] - Prevent resource leak in hudson.XmlFile#readRaw() in the case of encoding issues. (#2518)

[JENKINS-39363,CID-1205051] - Prevent resource leak in hudson.XmlFile#readRaw() in the case of encoding issues.

[JENKINS-39232] Walk the DelegatingComputerLauncher instances when checking if JNLPComputerLauncher (#2602)

* [JENKINS-39232] Walk the DelegatingComputerLauncher instances when checking if JNLPComputerLauncher

* [JENKINS-39232] Add a system property to enable legacy plugins to continue to work until they get fixed

* [JENKINS-39232] Be more forgiving of plugins

* [JENKINS-39232] Yet more forgiveness of plugins but define the forward contract

* [JENKINS-39232] Provide diagnostics when this issue is encountered

- Since the failure of strict verification is an issue, we should log it as a warning always

* Add viewport meta tag

Enables better responsiveness on mobile devices

* fix: Use self-closing tag

* Remove minimum-scale for best accessibility

* [JENKINS-26940] Print message when installer isn't applicable

* [JENKINS-26940] Only print when none found, add test

* Load i18n resource bundles from plugins if not found in jenkins core

Signed-off-by: Thorsten Scherler <scherler@gmail.com>

* Issue 404 response for missing i18n resource bundles

Currently issues a 200 with an "error" response payload. This change still issues the error response payload, but also sets the HTTP response.

Signed-off-by: Thorsten Scherler <scherler@gmail.com>

* [JENKINS-35845] Fix test since we return now a 404

* [JENKINS-35845] add test for getting locale from plugin. fix comments from oleg.

* [JENKINS-35845] Fix description

* [JENKINS-35845] Update PR with comments from Oleg

* [JENKINS-35845] Add feedback from tom

* eslint - formating changes and fix offences

* eslint - formating changes and fix offences

* [JENKINS-35845] remove code concerning 404 response. Fix resourceBundle test by prevent NPE to happen

* [JENKINS-35845] Link to issue on which we introduced the test

[FIXED JENKINS-38960] Deprecate getIconFilePathPattern and switch to IconSpec

* [JENKINS-36871] Switch to the new JnlpProtocolHandler based implementation

Todo

- [ ] Restore the cookie behaviour (but done right this time)
- [ ] Perhaps investigate issuing clients with TLS certificates (but would require a UI for managing them)

* [JENKINS-36871] License headers and javadocs

* [JENKINS-36871] Restore cookie handling

* [JENKINS-36871] Integrating Agent discovery components

* [JENKINS-36871] Pick up remoting 3.0-SNAPSHOT

* [JENKINS-36871] Pick up newer snapshot

* [JENKINS-36871] Oleg wants to log an exception that cannot happen

Placate the JDK 9 compiler

[FIXED JENKINS-31768] - Remove monitor lock from setNumberExecutors to avoid deadlock

Cleaning up @since TODO / @since XXX

[FIXED JENKINS-35967] - Make User#isIdOrFullnameAllowed() more robust against restricted usernames (#2413)

This change hardens username verification in user creation commands. See the issue to get rexamples.

https://issues.jenkins-ci.org/browse/JENKINS-35967

* Avoid deprecated findbugs annotations

* One more forgotten annotation