Add an "empty" limits_template

[loood]

Would like to see a template that has nothing in it except for the "# This file is managed by Puppet. Do not edit!" messages.

[saz]

@loood What's the idea behind it?

[loood]

Want to manage /etc/security/limits.conf to be basically empty except for that header as all configured limits are actually being written to inside the /etc/security/limits.d directory instead.

[saz]

There's now an empty template available generic_empty.erb