Add facades fullpath autocomplete (#437)

* Add method to retrieve namespace of extended class

* Regroup classes by namespace of the class they extends

* Restore facades shortnames

src/Generator.php

@@ -209,7 +209,7 @@ class Generator
                     $alias->addClass($this->extra[$name]);
                 }
 
-                $namespace = $alias->getNamespace();
+                $namespace = $alias->getExtendsNamespace() ?: $alias->getNamespace();
                 if (!isset($namespaces[$namespace])) {
                     $namespaces[$namespace] = array();
                 }