[FIXED JENKINS-24625] Set background color on input elements

[FIXED JENKINS-21881] System property for disabling X-Frame-Options

Enlarge and move Jenkins head icon

[FIXED JENKINS-6153] Add description for label atoms

[FIXED JENKINS-19764] Ensure parent dir of new builds dir exists.

Since ConsistentHash is written as a mutable class, I think a better way to fit the existing design is to provide a bulk add operation.
It already has several methods to that end, so I just added one more that's needed for our purpose.

Incorrect link to master node on label page

invoking add(Node, replica) for all nodes rebuild the internal Table many times. Using a builder, Table is only created (and sorted) once
also avoid creating a fresh new Hash object (java 8 lambdas, I miss you)