* new methods
privileges.categories.filter
privileges.topics.filter
privileges.posts.filter
they take a list of ids and a privilege, and return the filtered list of
ids, faster than doing async.filter and calling the db for each id.
* remove event listeners on recent page before adding
* group.exists works for both single group names and arrays
* helpers.allowedTo works for both a single cid and an array of cids
* moved filter:topic.post hook right before topic creation.
* moved filter:topic.reply hook right before topic reply.
-isMemberOfSets returns true/false instead of 1/0
-when loading the posts of a topic only get the userdata for each user
once, before this commit if a topic had 10 posts from 2 different users
we were getting the user data for each user 5 times (drunk)
-getVoteStatusByPostIDs and getFavouritesByPostIDs no longer make
pids.length calls to the db, they use isMemberOfSets now
-getUserInfoForPost renamed to getUserInfoForPosts and doesnt make
uids.length calls to db, uses getMultipleUserFields instead
