[FIXED JENKINS-20071] Upgrade bundled versions of credentials and ssh-slaves so we can assume <c:select/> available

Integrating the stapler fix.

Noting that various DirScanner implementations handle this inconsistently.

[FIXED JENKINS-18836][FIXED JENKINS-18879][FIXED JENKINS-19619] Upgrade trilead-ssh to version with the fix

Both are shown if defined. The edit description link only applies to View.description.
Properly handle a ViewGroup other than Jenkins itself, such as a folder.

[FIXED JENKINS-19920] Using selfReference to mean “none” from nextBuild/previousBuild was just asking for trouble.
JENKINS-16194 and an analogous but opposite bug fixed more simply by introducing a separate NONE constant.
Also numberOnDisk did not get updated properly after a build was deleted, causing double loading of build records in some cases.

[FIXED JENKINS-19251] Use hashes rather than modification time to determine if Maven agent JARs are up to date.

- Adds an option to the Global Security screen to hide the remember me checkbox
- A crafty user could use their browser to re-insert the form field and thereby get Jenkins to set the
  remember_me cookie on their browser, but this option should cover the 99.9% case.

This reverts commit 647695e2.

This reverts commit 647695e2.

[FIXED JENKINS-19613] 49c731fc made PROXY_HEADER static under the assumption that XStream would treat that like a missing field.
Unfortunately it threw an error instead, breaking startup; fixed by renaming the constant.

- This is an initial version of the feature.
- The information about slave names is still exposed via label autocomplete