Fetch source data: list Danbooru artist tag; elim duplicated code.

* In the `Fetch source data` box, list the Danbooru artist tag(s) that
  were found beside the artist name.

* Unify `Fetch source data` code that was duplicated between the
  uploads page and the post show page.

app/assets/stylesheets/specific/posts.scss

@@ -494,22 +494,6 @@ div#c-posts {
         color: gray;
       }
     }
-
-    div#source-info {
-      margin: 1em 0;
-      padding: 1em;
-      border: 1px solid gray;
-
-      p {
-        margin: 0;
-      }
-
-      ul {
-        a {
-          margin-right: 1em;
-        }
-      }
-    }
   }
 
   div#quick-edit-div {
@@ -529,6 +513,29 @@ div#c-post-versions, div#c-artist-versions {
   }
 }
 
+div#c-posts, div#c-uploads {
+  /* Fetch source data box */
+  div#source-info {
+    margin: 1em 0;
+    padding: 1em;
+    border: 1px solid gray;
+
+    p {
+      margin: 0;
+    }
+
+    > ul {
+      display: none;
+
+      .source-tags {
+        a {
+          margin-right: 1em;
+        }
+      }
+    }
+  }
+}
+
 div#c-explore-posts {
   a.desc {
     font-weight: bold;