Improve performance of "Mark all topics as read"

At the current time we did optimization of "Mark all read" by adding an ability to mark all forum as read. But at the same time we can improve performance of this functionality:

• When user opens topic that doesn't have changes since all forum has been marked as read, we shouldn't save an information about last read post in database.

acceptance criteria:
1) User marks all topic as read on forum. Opnes topic (which has no new topics since the mark all as read). in the database, the table LAST_READ_POST should not be an entry for the user, and the topic
2) User1 marks all topic as read on forum. User2 creates new post in topic. User1 opnes that topic (which has new posts since the mark all as read). in the database, the table LAST_READ_POST should contain an entry for the user and the topic
3) User marks all topics as read on forum. User creates new post in topic. In the database, the table LAST_READ_POST should has an entry for the user, and the topic