Corrected JUI comment tags in less/css/js files

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32345

Made the Joomla JUI comments in the media files use the same syntax everywhere.

Also the current syntax in less files caused some issues with some automated less compilers, leaving the ```/* >>> JUI >>> */``` comments in the compiled css files.

New syntax fixes that: 
```
// > Joomla JUI
...
// < Joomla JUI
```