implements AES encryption and decryption algorithms
see @link http://java.sun.com/developer/technicalArticles/Security/AES/AES_v1.html
see @link http://stackoverflow.com/questions/992019/java-256bit-aes-encryption
Servlet implementation class ajaxRqst
handles the different request from a web client which wants to give orders to a drone
and it handles administrator queries to manage users' profiles