Enlarge and move Jenkins head icon

Enlarge and move Jenkins head image a bit to be flush with the bottom of
the header bar.
Refactor CSS (top > bottom align)

Refactor CSS to make header images relative to the bottom of the header
bar rather than relative to the top.
Merge remote-tracking branch 'upstream/master'
[FIXED JENKINS-21881] System property for disabling X-Frame-Options
[JENKINS-21881] Add test
Exposing this to use it from other places that use channels
[FIXED JENKINS-24625] Set background color on input elements
Merge pull request #1360 from sfarbota/master

Enlarge and move Jenkins head icon
Merge pull request #1391 from daniel-beck/JENKINS-21881

[FIXED JENKINS-21881] System property for disabling X-Frame-Options
Noting #1360, #1391
Updated since
Merge pull request #1394 from quinox/master

[FIXED JENKINS-24625] Set background color on input elements
Noting #1394
[FIXED JENKINS-24614] Broken format string in Hebrew console output
Noting 07fd5fa
[maven-release-plugin] prepare release jenkins-1.580
[maven-release-plugin] prepare for next development iteration
updated changelog for release
updated changelog as a part of the release
merged back the RC branch