Updated all templates to use "@variable_name" to get rid of "deprecated" warnings

Updated all templates to use '@variable_name' to get rid of these warnings:

Warning: Variable access via 'title' is deprecated. Use '@title' instead.
template[/etc/puppetlabs/puppet/modules/pxe/templates/menu.erb]:1
   (at /etc/puppetlabs/puppet/modules/pxe/templates/menu.erb:1:in `block in result')