Docs + some variable changes

doc/Extensions/Network-Map.md

@@ -0,0 +1,17 @@
+# Network Map
+
+## LibreNMS has the ability to show you a network mab based on:
+
+- xDP Discovery
+- MAC addresses
+
+By default, both are are included but you can enable / disable either one using the following config option:
+
+```php
+$config['network_map_items'] = array('mac','xdp');
+```
+
+Either remove mac or xdp depending on which you want.
+
+A global map will be drawn from the information in the database, it is worth noting that this could lead to a large network map. 
+Network maps for individual devices are available showing the relationship with other devices.