PERF: shift most user options out of the user table

As it stands we load up user records quite frequently on the topic pages,
this in turn pulls all the columns for the users being selected, just to
discard them after they are loaded

New structure keeps all options in a discrete table, this is better organised
and allows us to easily add more column without worrying about bloating the
user table

app/models/user_option.rb

@@ -0,0 +1,29 @@
+class UserOption < ActiveRecord::Base
+  self.primary_key = :user_id
+  belongs_to :user
+  before_create :set_defaults
+
+  def set_defaults
+    self.email_always = SiteSetting.default_email_always
+    self.mailing_list_mode = SiteSetting.default_email_mailing_list_mode
+    self.email_direct = SiteSetting.default_email_direct
+    self.automatically_unpin_topics = SiteSetting.default_topics_automatic_unpin
+    self.email_private_messages = SiteSetting.default_email_private_messages
+
+    self.enable_quoting = SiteSetting.default_other_enable_quoting
+    self.external_links_in_new_tab = SiteSetting.default_other_external_links_in_new_tab
+    self.dynamic_favicon = SiteSetting.default_other_dynamic_favicon
+    self.disable_jump_reply = SiteSetting.default_other_disable_jump_reply
+    self.edit_history_public = SiteSetting.default_other_edit_history_public
+
+
+    if SiteSetting.default_email_digest_frequency.to_i <= 0
+      self.email_digests = false
+    else
+      self.email_digests = true
+      self.digest_after_days ||= SiteSetting.default_email_digest_frequency.to_i
+    end
+
+    true
+  end
+end