Fix frame data records being created for non-ugoira posts.

* Prevent non-ugoira posts from getting dummy frame data records with
  all the columns set to null.
* Make `data` and `content_type` columns NOT NULL, since they should
  always be present.
* Remove the timestamps while we're at it, since they don't seem
  necessary for anything.

app/models/upload.rb

@@ -112,7 +112,7 @@ class Upload < ActiveRecord::Base
         post.distribute_files
         if post.save
           CurrentUser.increment!(:post_upload_count)
-          ugoira_service.process(post)
+          ugoira_service.process(post) if is_ugoira?
           update_attributes(:status => "completed", :post_id => post.id)
         else
           update_attribute(:status, "error: " + post.errors.full_messages.join(", "))