BugTrack/2188 Define List layout by CSS instead of ini file

BugTrack/2188 Define List layout by CSS instead of ini file

* Define List styles by CSS instead of default.ini file
  * Add list-indent1, 2 and 3: that is express indent-distance to parent list
* In default.ini.php, $_ul_margin, $_ol_margin and $_dl_margin must be 1
  * These are used as indent leaping level calclation source
  * $_list_pad_str = ' class="list%d list-indent%d"';
    * 2nd param of sprintf($_list_pad_str, $1, $2) is exactly indent-level.
* This replacement from PHP logic to CSS is completely compatible
  with existing list logic that contains ls2 plugin
  and PukiWiki core list logic.