Change plugin to addon

change the use of plugin to addon where appropriate.

src/Model/GContact.php

@@ -969,7 +969,7 @@ class GContact
 	/**
 	 * @brief Fetches users of given GNU Social server
 	 *
-	 * If the "Statistics" plugin is enabled (See http://gstools.org/ for details) we query user data with this.
+	 * If the "Statistics" addon is enabled (See http://gstools.org/ for details) we query user data with this.
 	 *
 	 * @param string $server Server address
 	 * @return void

src/Model/User.php

@@ -390,7 +390,7 @@ class User
 			$photo = avatar_img($email);
 		}
 
-		// unless there is no avatar-plugin loaded
+		// unless there is no avatar-addon loaded
 		if (strlen($photo)) {
 			$photo_failure = false;