Alternate <hr> color for content pages

services/web/public/stylesheets/app/content_page.less

@@ -6,4 +6,7 @@
   a:not(.btn) {
     color: @link-color-alt;
   }
+  hr {
+    border-color: @hr-border-alt;
+  }
 }

services/web/public/stylesheets/core/ol-variables.less

@@ -53,6 +53,7 @@
 @link-active-color      : @ol-dark-green;
 @link-hover-color       : @ol-dark-blue;
 @hr-border              : @ol-blue-gray-1;
+@hr-border-alt          : @gray-lighter;
 
 // Button colors and sizing
 @btn-border-width        : 0;