ZF-4425: Create demo code for using secure AuthSub

Description

Secure AuthSub now works. Create some demo code that uses it.

Comments

Sample code is available here: http://framework.zend.com/svn/framework/…

and Secure AuthSub is documented here: http://code.google.com/apis/gdata/authsub.html

Marking as fixed.

Fix Version: 1.7.2

I've also created ZF-7064 to add documentation to the reference manual for this.