Made li list style dots more specific

We set all li elements to use list-style disc, but it was affecting our
navbar.  Changed it to use a specific class in the crop hierarchy (where
we actually cared about it).

app/assets/stylesheets/bootstrap_and_overrides.css.less

@@ -165,6 +165,6 @@ p.stats {
   }
 }
 
-li {
+li.crop-hierarchy {
   list-style-type: disc;
 }

app/views/crops/_hierarchy.html.haml

@@ -1,6 +1,6 @@
 %ul
   - display_crops.each do |c|
-    %li
+    %li.crop-hierarchy
       = link_to c, c
       - if c.varieties.present?
         - c.varieties.each do |v|