Add .container-fluid variation for full-width containers and layouts

/cc #10711 #9862

less/grid.less

@@ -2,7 +2,11 @@
 // Grid system
 // --------------------------------------------------
 
-// Set the container width, and override it for fixed navbars in media queries
+
+// Container widths
+//
+// Set the container width, and override it for fixed navbars in media queries.
+
 .container {
   .container-fixed();
 
@@ -17,12 +21,30 @@
   }
 }
 
-// mobile first defaults
+
+// Fluid container
+//
+// Utilizes the mixin meant for fixed width containers, but without any defined
+// width for fluid, full width layouts.
+
+.container-fluid {
+  .container-fixed();
+}
+
+
+// Row
+//
+// Rows contain and clear the floats of your columns.
+
 .row {
   .make-row();
 }
 
+
+// Columns
+//
 // Common styles for small and large grid columns
+
 .make-grid-columns();
 
 
@@ -76,4 +98,3 @@
   .make-grid(@grid-columns, lg, push);
   .make-grid(@grid-columns, lg, offset);
 }
-