define roles: MDL-16966 etc. polishing the new roles UI following a meeting with Martin.

* Move the show/hide advanced button a bit down the page.
* Improve save button caption when creating a role.
* Don't show defaults on the basic define roles screen.
* Explain the background shading on the advanced roels screen.
* Fix the problem with the risks link to Moodle docs.
* Help icon by the permissions column heading.
* Tables with rotated <th>s, make them vertical-align: bottom.
* Rename explain.php and explainhascapability.php to check.php and explain.php
* Tool tips on the number headers in the explain table.
* Explain table - role names were missing.
* Allow link_to_popup_window to work with full URLs.

lib/javascript-static.js

@@ -514,7 +514,10 @@ function getElementsByClassName(oElm, strTagName, oClassNames){
 }
 
 function openpopup(url, name, options, fullscreen) {
-    var fullurl = moodle_cfg.wwwroot + url;
+    var fullurl = url;
+    if (!url.match(/https?:\/\//)) {
+        var fullurl = moodle_cfg.wwwroot + url;
+    }
     var windowobj = window.open(fullurl,name,options);
     if (fullscreen) {
         windowobj.moveTo(0,0);