Expose User object to Plugin API

Closes #379
Changes #378

lib/api.js

@@ -1,6 +1,7 @@
 var hap = require("hap-nodejs");
 var hapLegacyTypes = require("hap-nodejs/accessories/types.js");
 var log = require("./logger")._system;
+var User = require("./user").User;
 
 // The official homebridge API is the object we feed the plugin's exported initializer function.
 
@@ -12,6 +13,9 @@ function API() {
   this._accessories = {}; // this._accessories[pluginName.accessoryName] = accessory constructor
   this._platforms = {}; // this._platforms[pluginName.platformName] = platform constructor
   
+  // expose the User class methods to plugins to get paths. Example: homebridge.user.storagePath()
+  this.user = User;
+  
   // expose HAP-NodeJS in its entirely for plugins to use instead of making Plugins
   // require() it as a dependency - it's a heavy dependency so we don't want it in
   // every single plugin.