Improve the performance of the application by storing extra information in the Topic Class

A lot of queries are performed for each answers from each topic from each forum to get some information like:

• the number of the comments from an answer
• the number of answers from a topic
• the number of the comments from a topic
  Instead we can have 2 number properties in the TopicClass to store the number of the answers from a topic and the number of the comments from a topic (the comments are objects in Answers documents). These properties should be updated at the creation and deletion of an answer or a comment.