Added a class which will build from 2 xml files - people, which tracks who has an nfc card and what their achievements are,
and the pi itself, which tracks what achievements the admin has put on the pi

this will also create the files if they don't exist, handle admin tasks like adding new achievements,
read the card and update/show the user's achievement status, or read the card and add a new user if they don't exist.

read.py takes this class and calls the read method of the class.
next commit will be admin which will let the admin users add achievements.