Update the structure of metadata for error/access logs

This now looks like:

```
site:
  log:
    access: /path/to/access.log
    error: /path/to/error.log
```
diff --git a/nginx/files/_log.conf b/nginx/files/_log.conf
index d95c6b1..b1c1a42 100644
--- a/nginx/files/_log.conf
+++ b/nginx/files/_log.conf
@@ -1,5 +1,5 @@
 {%- from "nginx/map.jinja" import server with context -%}
 {%- set site = salt['pillar.get']('nginx:server:site:'+site_name) %}
 
-  access_log {{ site.get('access_log', server.log_dir + '/' + site_name + '-access.log') }};
-  error_log {{ site.get('error_log', server.log_dir + '/' + site_name + '-error.log') }};
+  access_log {{ site.get('log', {}).get('access', server.log_dir + '/' + site_name + '-access.log') }};
+  error_log {{ site.get('log', {}).get('error', server.log_dir + '/' + site_name + '-error.log') }};
diff --git a/nginx/files/nginx.conf b/nginx/files/nginx.conf
index fcda3fd..c70f7a0 100644
--- a/nginx/files/nginx.conf
+++ b/nginx/files/nginx.conf
@@ -35,8 +35,8 @@
         # Logging Settings
         ##
 
-        access_log {{ server.get('access_log', server.log_dir + '/access.log') }};
-        error_log {{ server.get('error_log', server.log_dir + '/error.log') }};
+        access_log {{ server.get('log', {}).get('access', server.log_dir + '/access.log') }};
+        error_log {{ server.get('log', {}).get('error', server.log_dir + '/error.log') }};
 
         ##
         # Gzip Settings