client/topics.js refactor

ability to dismiss all flags
postCount only used once
fix pagination going to 404 if new post creates a new page
closed #2424
adding missing file, re: #2424
fix rename to multi
Merge branch 'master' of https://github.com/NodeBB/NodeBB
fixed maintenance mode page not working with new CSRF implementation, #2424
shorter getTeasers
use send for child process
disconnect on error too
closes #2316
shorther