include/vnc.js: dynamic load without document.write.

Instead of using document.write to load scripts, use createElement to
create and append script tags. document.write is problematic in a lot
of situation and in particular is not allowed in a Chrome
extension/packaged app.

Also, in webutil.js, instead of calling init_logging during parsing of
include/webutil.js, rely on the caller to do this. The problem is that
calling init_logging on parse tries to call Util logging functions and
the new model of dynamic load may not having Util loaded by the time
webutil is parsed.