Adjust z-index for #search-box-completion to appear over the breadcrumb

Applied the change from Olav Reinert.

Earlier Jenkins advertised being in port 80 regardless
what port it was really listening.

Also added registration to service _http._tcp which makes
Jenkins appear in Bonjour bookmarks of the Safari browser.

WorkspaceSnapshot now uses the tar.gz format to handle symlinks
correctly.

Tar/untar now correctly supports symlinks.

Fixed the file overwrite problem on Windows.

Absolutizing on the server side is easier and more compact.

http://jenkins.local/job/JOBNAME/configure will become
10%-faster in Chrome 14 and 20%-faster in IE 9.

$(e).next() may return undefined.
If 2nd argument of insertBefore is undefined,
IE9 complains "SCRIPT87: Invalid argument".
To insert newChild at the end, 2nd argument should be null.
http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113/core.html#ID-952280727

If we fail to obtain the update center metadata, don't keep retrying
every 15 seconds, but use exponential time out to avoid overloading
our server in case of a problem.