/dmails: remove unused search[owner_id] param.

/dmails is restricted to viewing dmails for CurrentUser only (due to
Dmail.visible in the index action). Remove owner_id from subnavbar links
in /dmails, and don't support it in /dmails?search[owner_id], since it
doesn't actually do anything.

Also removes related dead methods and fixes tests that didn't test owner_id properly.

app/helpers/dmails_helper.rb

@@ -2,11 +2,23 @@ module DmailsHelper
   def dmails_current_folder_path
     case cookies[:dmail_folder]
     when "sent"
-      dmails_path(:search => {:owner_id => CurrentUser.id, :from_id => CurrentUser.id}, :folder => "sent")
-    when "all"
-      dmails_path(:search => {:owner_id => CurrentUser.id}, :folder => "all")
+      sent_dmails_path
+    when "received"
+      received_dmails_path
     else
-      dmails_path(:search => {:owner_id => CurrentUser.id, :to_id => CurrentUser.id}, :folder => "received")
+      all_dmails_path
     end
   end
+
+  def all_dmails_path(params = {})
+    dmails_path(folder: "all", **params)
+  end
+
+  def sent_dmails_path(params = {})
+    dmails_path(search: {from_id: CurrentUser.id}, folder: "sent", **params)
+  end
+
+  def received_dmails_path(params = {})
+    dmails_path(search: {to_id: CurrentUser.id}, folder: "received", **params)
+  end
 end