Add ability to mark all topics read in recent activity

As a user I'd like to have ability to mark all topics as read, not only topics for particular branches.
Acceptance Criteria:

• A link should appear right above pagination buttons in recent activity and on top of main page.
• After pressing the link, all topics in all branches are marked as read.
• This shouldn't take more than 2 secs.

Tech details:

• We're having a LAST_MARKED_ALL_AS_READ column in JC_USER table which is filled with now() when user presses it.
• When pressing the Mark All As Read all records from LAST_READ_POST_INDEX are removed since we can depend upon column in JC_USER.
• When we show the topics, we're first checking whether their last created post date happened before than LAST_MARKED_ALL_AS_READ,
  • If yes, then those topics have been read.
  • If topic was created after marking everything read, then we should check LAST_READ_POST_INDEX for the records
• We still use LAST_READ_POST_INDEX and add record to it when user reads new posts of the topic.