Fixed multiple issues for CloudSpokes challenge 2572

Demo URL - http://67.20.109.73//dev/php_api/DocuSignSample/senddocument.php

===================
Features Tested/ Verified
===================

* This is the list of features I verified/ tested

- Send Document (verified all parameters and email sending)
- Send a template
- Embed DocuSign
- Get Status and Docs - Verified all operations including ViewRequestStatus, Download PDF and Start Signing

===================
Issues Fixed
===================
* Current code throws a 403 error if you hit 'Choose Template' and there is no template available. I added a defensive check there.
* Removed a lot of redundant code - header code was copied in all files, moved it to a single php file and included that
* Cosmetic Change - Changed 'logout' to 'Logout'
* Changed Footer links to open in a new window