WICKET-5615 UploadProgressBar does not show up if no FileUploadField is
given
WICKET-5617 Make it possible to set markup id to CSS header contributions
WICKET-5605 Store browser capabilities in local variables in wicket-event-jquery.js

Remove Wicket.Browser.isIE(LessThan)7 methods. IE7 is not supported for a long time
WICKET-5616 CLONE - ModalWindow is not visible in Safari when opened from a link at the bottom of a large page

Revert https://github.com/apache/wicket/commit/61ebe2dbd55ff2ff5ac6f73909708021bb1acf4d as suggested by Luke Niesing and Jered Myers

(cherry picked from commit c70a5e00917503a98e27535c5057d1c8630d5060)