Added a second rake task to generate the session store file.

`rake generate_session_store`

A lot of people think `rake config/initializers/session_store.rb` needs to
have an existing session_store.rb file in order to generate it.  This task
will make it easier to explain and document.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3267 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/tasks/initializers.rake

@@ -22,3 +22,6 @@ ActionController::Base.session = {
 EOF
   end
 end
+
+desc 'Generates a configuration file for cookie store sessions.'
+task :generate_session_store => ['config/initializers/session_store.rb']