[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?)