Improved tables, Separated tables into core and site segments, rules and pages

Update index.php, sidebar.php, and 7 more files...

scss/nibblepoker.scss

@@ -60,6 +60,7 @@
 @import 'core/position';   // /!\ Needs improvement !!!
 @import 'core/overflow';   // Defines generic overflow rules (.o-hidden, .ox-scroll, ...)
 @import 'core/lists';
+@import 'core/table';
 
 /* Core > Rounding */
 @import 'core/rounding/global';