Fixed small bugs in search services
Fixes to SqlSelectStatement
Fixed date: post search token
New Sql operators, because they may come in handy
Changed /comments behaviour

Instead of showing comments chronologically, group them into posts, then sort
the posts by last comment date. Reason: improved comment context delivery
makes discussion bumping possible (no matter how old it is) and discussion is
what comments are about.

Comment count is limited to 5 per post.
Faster preloading
Added comment preloading
Better debug
Faster special:liked/disliked computing
Faster entity counting

All ORDER BY is discarded when counting entities in search services.