[FIXED JENKINS-21716] Set Content-Type header for env-vars.html

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>

[FIXED JENKINS-20086] Allow disabling use of default exclude patterns (.git, .svn, etc.)

Reference: https://trello.com/c/doFFMdUm/46-filepath-getcomputer

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>

[JENKINS-23595] - Fix makeFlash script bug with ImageMagick v6.7.9+

Fix a NPE when the 'properties' element is missing from the form's JSON

switched off alpha before colorizing temporary gifs when making animated balls. prevents colorize from applying fill to alpha channel. alpha is turned back on after colorize operation

[FIXED JENKINS-23481][FIXED JENKINS-23551] Send onOffline notification to master computer prior Jenkins restart

[FIXED JENKINS-23481][FIXED JENKINS-23551] Send onOffline notification to master computer prior Jenkins restart.

Introduces new overload `ComputerListener.onOffline(Computer, OfflineCause)`.

[FIXED SECURITY-134] Restrict access to admin monitor info page

[FIXED JENKINS-23526] Tolerate 'null' result when used creatively

- Replaces thick shadow with a fuzzy shadow.

- adds more padding

- adds a pointer cursor to indicate the items are clickable.

Previously the inputs would bleed behind the help text. They were still
clickable but this is not a desirable visual effect.