remove acts_as_paranoid, use .trash! , .recover! and .with_deleted as needed

makes upgrading to rails 4 possible

app/controllers/invites_controller.rb

@@ -33,7 +33,7 @@ class InvitesController < ApplicationController
 
     invite = Invite.where(invited_by_id: current_user.id, email: params[:email]).first
     raise Discourse::InvalidParameters.new(:email) if invite.blank?
-    invite.destroy
+    invite.trash!
 
     render nothing: true
   end

app/controllers/posts_controller.rb

@@ -128,7 +128,7 @@ class PostsController < ApplicationController
   def recover
     post = find_post_from_params
     guardian.ensure_can_recover_post!(post)
-    post.recover
+    post.recover!
     render nothing: true
   end
 

app/controllers/topics_controller.rb

@@ -100,7 +100,7 @@ class TopicsController < ApplicationController
   def destroy
     topic = Topic.where(id: params[:id]).first
     guardian.ensure_can_delete!(topic)
-    topic.destroy
+    topic.trash!
     render nothing: true
   end