Fix: Only print Google Analytics scripts on transaction results footer

We weren't making use of the $display_to_screen variable here when we should have been.  It was causing issues where transaction_results() would be called on order status changes, triggering this output when it was inappropriate.
Cart widget missing closing </div> tag. Fixes #97.
- passsing the post_id through

Seems silly that WordPress allows a post_id in get_the_title and when
WPEC provides it's own function it doesn' allow the parameter. In
general we should be passing the params that WordPress expects unless
it's retarded.
Add context for "Tracking ID" strings.
More proper context for all Tracking ID strings.

Also fix one instance where _ex() should be used instead of _x()
in marketing.php.