QR code generator class

This class can be used to generate QR Code images using Google Chart API. It can send an HTTP request to the Google Chart API Web server to request the generation of a PNG image that represents the QR code graphic for a given information snippet. Currently the class can request the generation of QR codes for information snippets of types: bookmark, text, SMS message, phone number, contact information, e-mail message, geo-location, WIFI access, i-appli metadata or abitrary content-type. The generated QR code image can be returned as a string, served for download or returned as an URL string.