Remove denyhosts support from 'tcpwrappers' role

denyhosts has been removed from Debian Sid/Jessie:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=732712
Rewrite of 'tcpwrappers' role

- tcpwrappers now use lists of hashes to manage entries in
  /etc/hosts.allow better;

- tcpwrappers configuration has been cleaned up and streamlined, you can
  now configure access using host lists similar to other roles (for
  example ferm), you can pass configuration to tcpwrappers directly from
  other roles via dependency variables;

- you might want to reset /etc/hosts.allow to original state and remove
  contents of /etc/hosts.allow.d/ before applying these changes. Not
  doing so should not cause any harm and will result only in duplicated
  entries;
Merge pull request #26 from drybjed/role/tcpwrappers

Updates in 'tcpwrappers' role