Add a template for vsftpd.conf

 * Most of its options are available as parameters for the class.
 * Added a couple of files with default options (chroot_list and user_list).
 * Documented all these options in init.pp, mainly through c&p from the .conf file.
As suggested by Alessandro, leave template variable empty.

That way, we don't mess with the different distros default configuration.
Merge pull request #2 from netmanagers/master

Added a template file