Implement support for disqus_category_id

issue on drupal.org: https://www.drupal.org/node/2304167
I thought that it would be a good idea if categories are automatically created according to the bundle name while creating the field and the user(site's moderator) does not have to explicitly a provide category. I guess most of the users wont care to categories comments (so we can do it automatically by this approach).
I tested this approach and category is created according to the content-type title (eg. article,etc) and for taxonomical terms according to the vocabulary title.