refactor guardian class for clarity & correctness

introduce NullUser to avoid type-checking
DRY up code
reduce number of multiple returns
remove some redundant/impossible logic branches
add pending test for possible bug
add test & fix for ability to flag archived posts
add #secure_category? method to topic class
Fix bug that prevented flagging of archived topics
Rename NullUser to AnonymousUser
DRY up can_<action>? methods
Fix some ownership logic, and a test, for Guardian
Merge pull request #879 from mattvanhorn/refactor_guardian

refactor guardian class for clarity & correctness
Refactor + Fix: Wasn't correctly loading activity streams. Code is a lot more Ember-y now.
Adding Apache2 + Passenger instead NGINX
Search Refactor: Let's use a class to keep track of our state rather
than passing params everywhere. Also make the private API private.
Search Refactor: Remove some manual SQL, make search data tables more idomatic Rails/AR
Merge pull request #880 from bsides/patch-1

Adding Apache2 + Passenger instead NGINX
Just fixed a typo and added a warning

Honest mistake I took from pasting it from my own system :)
Merge pull request #882 from bsides/patch-1

Just fixed a typo and added a warning
minor copy changes
User tracking state implementation progress for live unread / new counts