* [JENKINS-43653] - Ensure AbstractItem#delete() NPE and RTE safety when checking executors.

This change adds missing NPE checks and also improves handling of Executables#getParentOf(), which may throw undocumented Runtime exceptions if Executable uses core API below 1.377 and does not implement getParent(). Executor#stop() has been also modified to explicitly handle the issue though there is still the same issue with estimated execution times.

* [JENKINS-43653] - Address comments from @jglick, restrict newly introduced API

* [JENKINS-43653] - Address comments from @stephenc

* [JENKINS-43653] - Cleanup "unrelevant" changes to make @stephenc and @jglick happy

* [JENKINS-43653] - Cleanup the leftover

* [JENKINS-43653] - Drop the changes in Executables

[JENKINS-42717] - Prevent NPE when a non-existent Default View is specified in the global config (#2815)

* [JENKINS-42717] - Document view management methods in Jenkins and ViewGroupMixIn

* [KENKINS-42717] - GlobalDefauldViewConfiguration should not fail with NPE when the view is missing

* [JENKINS-42717] - Draft the direct unit test

* [JENKINS-42717] - Fix the tes implementation

* [JENKINS-42717] - Make FormException localizable

* [JENKINS-42717] - Fix te build glitch

* [JENKINS-42861] - Properly deprecate the HudsonExceptionNote implementation

It is a replacement of the original fix in https://github.com/jenkinsci/jenkins/pull/2808.

The implementation provides deprecates the annotation of the new stacktraces, but it retains the binary and the persisted data compatibility, which were missing in the original PR.
In the longer-term the hyperlinks should be replaced by the best possible equivalent (JIRA search, grepcode or whatever).

* [JENKINS-42861] - Cleanup the deprecated functionality

[JENKINS-21695] - The CompressionFilter.uncaughtExceptionHandler must not attempt to write to a committed response. (#2834)

- Plugins should really be expecting it, but as historically they have not, may as well convert to IOE for them

[FIXED JENKINS-35160] - Job deletion: Wait up to 15 seconds for interrupted builds to complete (#2789)

* [FIXED JENKINS-35160] Wait up to 15 seconds for interrupted builds to complete

- Also now aware of concurrent builds

* [JENKINS-35160] Tests are good, they catch bugs

* [JENKINS-35160] We should do the interrupt for any Item not just Jobs

* [JENKINS-35160] s/DeleteBlocker/ItemDeletion/g

Left over references before I settled on a better name

* [JENKINS-35160] Switch to Failure for better HTML rendering

* [JENKINS-35160] Align the i18n key with owning class

(cherry picked from commit a34479c4)

(cherry picked from commit 43d612f9)

(cherry picked from commit 249dfb13)

(cherry picked from commit 5d920577)

(cherry picked from commit d0d9216f)

(cherry picked from commit 5f5f8800)

(cherry picked from commit 83835770)

* Clean up usages of IOUtils.closeQuietly and related calls predating Java 7.

* Review comments from @oleg-nenashev.

* Noticed another place where try-with-resources would protect against a potential leak.

Also make sure we don't mark the Computer as used so that we kill any
executors that may be related to it somehow.

* [FIXED JENKINS-40848] Introduce status indicator for skipped download job

* [JENKINS-40848] Stick to existing code-flow as that is proved to work

* [JENKINS-42645] Case insensitive search by default

* [JENKINS-42960] Search in FixedSet more locale friendly

String.equalsIgnoreCase is safer than toLowerCase when non English
locales are used.

* [JENKINS-42645] Review remarks

Something¹ seems to interrupt the HTTP duplex service thread,
and Jetty apparently deals poorly with interruptions.
So introduce an extra sleep to soak up the interrupt.

¹Who? http://stackoverflow.com/questions/2126997/who-is-calling-the-java-thread-interrupt-method-if-im-not#comment40865453_2127397

Jetty 9.4.3.v20170317 refuses to set an empty HTTP header, leading to cryptic client errors since Hudson-Duplex is missing.

Making interrupt of `build -s` work in `-http` mode.
Does not solve `ReadPendingException`s.

Obsolete with Java 8. Permanent generation was removed.