Use semantic HTML classes in table actions

Note the CSS could probably be improved to avoid duplication with other
button style definitions. However, that's fine because we're going to
change the style of the links soon.

For the same reason, I haven't bothered to style every single link the
way it was until now.

app/assets/stylesheets/admin/table_actions.scss

@@ -9,4 +9,17 @@
   > p {
     align-self: flex-start;
   }
+
+  a {
+    @include button($style: hollow);
+    border-color: $link !important;
+    color: $link !important;
+    font-size: $base-font-size;
+    margin-bottom: 0;
+
+    &.destroy-link {
+      border-color: $alert-color !important;
+      color: $alert-color !important;
+    }
+  }
 }