[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

[FIX JENKINS-23244] Slave build history page has no data and spawns a ton of very long-lived blocking threads on the master (#2584)

Mainly commit are doing two things:
1) Show only selected (visible) builds
2) Query build one-by-one - not it parallel

* [FIXED JENKINS-38650] - Cleanup spelling in CLi commands.

Also adds some javadoc and since definitions.

* [JENKINS-38650] - Move common warning message to the constant

* [JENKINS-38650] - DeleteViewCommand should also use the constant string

* [JENKINS-38650] - Rename the constant in order to make the name more explicit

2.61 does not exist, there was an issue during the release
Changes in 2.62: https://github.com/jenkinsci/remoting/blob/stable-2.x/CHANGELOG.md#2622

* [JENKINS-38539](https://issues.jenkins-ci.org/browse/JENKINS-38539) - 
Stability: Turn on SO_KEEPALIVE and provide CLI option to turn it off again.
(https://github.com/jenkinsci/remoting/pull/110)
* [JENKINS-37539](https://issues.jenkins-ci.org/browse/JENKINS-37539) - 
Prevent <code>NullPointerException</code> in <code>Engine#connect()</code> when host or port parameters are <code>null</code> or empty.
(https://github.com/jenkinsci/remoting/pull/101)
* [CID-152201] - 
Fix resource leak in <code>remoting.jnlp.Main</code>.
(https://github.com/jenkinsci/remoting/pull/102)
* [CID-152200,CID-152202] - 
Resource leak in Encryption Cipher I/O streams on exceptional paths.
(https://github.com/jenkinsci/remoting/pull/104)

[JENKINS-23786] Permit the Shell plugin to set a build result as unstable via a return code

Call hpi:record-core-location

* [JENKINS-38678] Remove properly administrative monitor

previous impl didn't work because ExtensionList#iterator() returns a
readonly iterator.

* Use foreach loop

refactor and fix

remove duplication and fix FB errors

fix integration tests

consistency fixes

consistency fixes

changed error message to warning

fix comment and warning message

fix comment

fix junit tests

fix junit tests

fix junit tests

fix junit tests

clean import

a commit to trigger jenkins checks

* Update XStream drive to improve performance in xml serilization/deserialization

According XStream FAQ (http://x-stream.github.io/faq.html#Scalability):

XStream is a generalizing library, it inspects and handles your types on
the fly. Therefore it will normally be slower than a piece of optimized
Java code generated out of a schema. However, it is possible to increase
the performance anyway:

* Write custom converters for those of your types that occur very often in
your XML.
* Keep a configured XStream instance for multiple usage. Creation and
initialization is quite expensive compared to the overhead of XStream
when calling marshall or unmarshal.
* Use Xpp3 or StAX parsers.

So, I decided to move from old Xpp to new Xpp3.

* Change other occurance of XppDriver to Xpp3Driver as well

[FIX JENKINS-38615] Add user to restart log message

[JENKINS-37098] Since tag cleanup

Declare .gitattributes and normalize line endings

That file will avoid users to file PR with wrong newline encoding.
I've tried to declare what seemed to be the most common extensions. It's
not strictly required, since the first line and the Git integrated
heurisitics would work just fine in general. But we're just adding a bit
more info here to lower chances to screw up.

[JENKINS-38651] Display actions created through TransientActionFactory in label view

See but very important  as not following this will result in :bugs: during code review