IE compatibility mode tweaks

Set "X-UA-Compatible" meta tag (MSIE browsers only - forces browser compatibility mode)
JS based warning if Document Mode doesn't match IE version (MSIE browsers only)
[FIXED JENKINS-20663] For now, go back to using ZipOutputStream from Ant that supports setting the filename encoding (present in java.util.zip only in Java 7+).
<l:icon> layout tag