further works on FreeBSD support

  * "$apache::conf_dir}/Includes" as $apache::confd_dir,
  * "$apache::conf_dir}/Modules" as $apache::mod_dir,
  * "$apache::conf_dir}/Vhosts" as $apache::vhost_dir,
  * added $mime_support_package parameter to apache::mod::mime class,
  * apache::mod::mime installs $mime_support_package package,
  * added $magic_file parameter to apache::mod::mime_magic class,
  * added 'default_confd_files.pp', and confd template infrastructure,
  * touched documentation (README.md),
  * other changes, not mentioned here