Was about to do a tiny bit of work in the cart calss part of the cart.class.php and noticed that the file would benefit from a little cleanup before I made changes.

* This commit deosn't have any logic changes other than the deprecated functions noted here.
* the template functions were moved to a distinct file.
* The cart class is now the only thing in the cart.class.php file.
The google checkout functions have been deprecated. Note that one google checkout function is a part of the
cart class.  That function has been deprecated in place.
To preserve backwards compatibility changed ordr of includes to give same result as prior to 3.8.14
Added a wpsc doing it wrong message if a direct include of cart.class.php is detected
Removed google checkout related call
Removed call to wpsc_google_checkout.

The wpsc_google_checkout function is still intact, but in the deprecated functions file.  It will display a warning when someone who has upgrades has a copy of the widget theme file in thier theme.
Merge pull request #991 from JeffPyeBrook/cart-class-to-its-own-file

Cart Class File Cleanup and Function Deprecation