change it so all topics MUST include a category, we store a special uncategorized category to compensate

this cleans up a bunch of internals and removes some settings

spec/components/trashable_spec.rb

@@ -7,12 +7,8 @@ describe Trashable do
     p1 = Fabricate(:post)
     p2 = Fabricate(:post)
 
-    Post.count.should == 2
-    p1.trash!
-
-    Post.count.should == 1
-
-    Post.with_deleted.count.should == 2
+    expect { p1.trash! }.to change{Post.count}.by(-1)
+    Post.with_deleted.count.should == Post.count + 1
   end
 end