Add role to install nfs-server, cleanup roles and configuration

- use generic media_dirs including vdr recdir, loop over them to
  create directories, configure samba, nfs, etc.
- add role to install an configure nfs-kernel-server
- cleanup roles
- add custom fact modules

roles/nfs-server/templates/nfs-exports.j2

@@ -0,0 +1,4 @@
+/srv *(rw,fsid=0,sync,no_subtree_check,all_squash,anongid={{ vdr.gid }},anonuid={{ vdr.uid }})
+{% for name, path in media_dirs.iteritems() %}
+{{ path }} *(rw,fsid={{ loop.index }},sync,no_subtree_check,all_squash,anongid={{ vdr.gid }},anonuid={{ vdr.uid }}{{ ',insecure' if nfs.insecure else '' }})
+{% endfor %}