[FIXED JENKINS-21448] Report number of jobs in any container

Follow up fix as pointed out by Daniel Beck.

This reverts commit 1fda95b6, reversing
changes made to 0fd39c44.

Daniel Beck confirmed that I wasn't supposed to merge both 1090 and
1091. After discussion with him, I'm taking 1090.

See: https://github.com/jenkinsci/jenkins/commit/1fda95b6aea55cb216074b18bbb34fd8708c64c0#commitcomment-5112285

Renamed "Run Command" to "Run Shell Command"

Conflicts:
	core/src/main/java/hudson/logging/LogRecorder.java
	core/src/test/java/hudson/logging/LogRecorderTest.java

[FIXED JENKINS-21386] Allow more specific loggers to reduce log level

Fix failed to start when removed

My recommended fix in response to https://github.com/jenkinsci/jenkins/pull/1093. This does not eliminate nor exclude the need for more generic pluggability, but it would at least address the security concern.

[JENKINS-17526] Relocating Jetty/Java tmpdir for Mac OS X.

Warn in the UI about short cycles in the day of month field for a crontab, which can have surprising behaviors near the end of a month.

Replaced “New Job” with “New Item” since various plugins (such as cloudbees-folder) add TopLevelItemDescriptor’s which do not produce Job’s.
(Might be feasible to automatically use “Job” or “Item” according to the most specific common supertype of all registered descriptors?)

When downloading a zip file with all of the artifacts, file descriptors
would be opened and never closed. This resulted in many leaked file
descriptors which would only be cleaned up the next time the garbage
collector was run.

For directories with a large number of files, the zip file would be
corrupted because an exception was thrown during the process of creating
the zip file when the process ran out of file descriptors. Jenkins was
then left in a very brittle state as random threads wouldn't be able to
open files or sockets anymore until the garbage collector was run.

[FIXED JENKINS-21371] Enhance SecurityRealm API to support queries of the group membership