Rename vhost and directory

Renamed to match new naming conventions.

We are using a wild card as the long form fo the server_name
is too long for the server_name_hash_bucket_size that is hardcoded
by the nginx module we are using.
Use parameter rather than hardcoded string

ext4mount should have been using the data_dir parameter rather
than the hard coded string which was left in mirror_enviornment.

Added data_dir param doc.
Add www_roots parameter to add dirs in data_dir

We have ensured that the data_dir exists and then we create
any defined www_roots. The file resources are setup to run
after the ext4mount so our www_roots do not get overwritten.
Merge pull request #2 from tombooth/nginx-vhost-naming

Nginx vhost naming