FreeBSD support

Initial support for FreeBSD. This is only roughly tested on FeeBSD (manually, few simple cases). Basically works under FreeBSD (at least with most settings default). Here is summary of what's inside:
  * "${apache::conf_dir}/Includes" as $apache::confd_dir for FreeBSD,
  * "${apache::conf_dir}/Modules" as $apache::mod_dir FreeBSD,
  * "${apache::conf_dir}/Vhosts" as $apache::vhost_dir FreeBSD,
  * new parameters in apache::params class: $root_group, $apache_package, $server_root
  * 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 to allow putting some files under ``conf.d/`` (``Includes/`` under FreeBSD) by default (FreeBSD's apache22 installs ``Includes/no-accf.conf`` for example but puppet normally would purge it afterward),
  * touched documentation (README.md),
  * other (minor) changes and additions,

What is still missing/needs more work:
  * can't correctly install packages for extra (not installed by default) apache modules, including php5 - this needs support for package compile/install options in package provider,
  * specs are given as is, not sure if they're correct (I have actually no knowledge on ruby/rspec and the testing infrastructure used for puppet, so forgive me please) - any help appreciated,
  * there are more things that I'm not sure about, they're commented as FIXME's, TODO's and XXX's in code,

I would be glad to run some automated tests, but need some guidance of where to star.