Use root_path for both the wordpress and wp-content roots in the nginx template

This eliminates the need for `directory` and `wp_directory` to be specified.
Remove nginx config for /files/, which is not used in WordPress anymore
Remove specific rules that are not used in our config
No need to add a slash to wp-admin requests
Use directory for each site as a unique ID rather than name, server_name, root_path, etc.

This simplifies the config a bit.
Move WP download to top of state file as it doesn't happen in the loop
First attempt at setting defaults for local database data
Use dict updating to update the site_args with defaults
s/db_name/database/
We should require that the database name be specified
Remove duplicate permissions set on www directory
Add documentation throughout the wordpress.sls file
Move nginx.conf to nginx.conf.jinja for templating
Change management of nginx.conf to be based on the template
Enable sendfile in production for nginx, disable in local
Syntax error when passing pillar data as context
Use a jinja template to manage xdebug configuration in development

This allows a remote host to be specified based on the environment.

Closes #47
Make the template of xdebug.ini rely on gateway_ip in the network.sls
Move xdebug config to webserver.sls behind a local environment check

This drops the need for a `devserver.sls` completely.
Remove mentions of devserver.sls