Add WebKit Nightly Archives, WebKit Nightly Start, and Downloads pages

Add WebKit Nightly Archives, WebKit Nightly Start, and Downloads pages
https://bugs.webkit.org/show_bug.cgi?id=155989

Reviewed by Timothy Hatcher.

* wp-content/plugins/sync-nightly-builds.php: Added.
* wp-content/themes/webkit/downloads.php: Added.
* wp-content/themes/webkit/functions.php:
* wp-content/themes/webkit/images/download.svg:
* wp-content/themes/webkit/images/spinner.svg: Added.
* wp-content/themes/webkit/nightly-archives.php: Added.
* wp-content/themes/webkit/nightly-start.php: Added.
* wp-content/themes/webkit/nightly.php:
* wp-content/themes/webkit/scripts/searchbuilds.js: Added.
(initsearch.xhrPromise.):
(initsearch):
(initsearch.displayResults.addEntry):
(initsearch.displayResults):
(initsearch.displayError):
(initsearch.clearErrors):
* wp-content/themes/webkit/style.css:
(input[type=text]):
(input[type=submit]):
(article .byline):
(article .abovetitle):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@198816 268f45cc-cd09-0410-ab3c-d52691b4dbfc