[FIXED JENKINS-21819] Add 'tail' functionality for files in WS

Some tools log so verbosely that the regular build log becomes barely usable. But when redirecting tool output to files in the workspace, they cannot easily be accessed during a build to see the current status, because `view` shows the entire file, and browsers rarely handle these well with >10MB file size.

This change adds a `tail` link next to `view` that only shows the end of the file.

Adds new system property `hudson.model.DirectoryBrowserSupport.tailKB` that will need to be added [to the wiki](https://wiki.jenkins-ci.org/display/JENKINS/Features+controlled+by+system+properties) once merged and released.