Template Inline Docs for shortcode-login.php

I think a few templates need some inline documentation, like this template for example. Just a thought.
Template documentation for history-downloads.php
Template documentation for history-purchases.php
Template Documentation for shortcode-register.php
Fixing template doc for history-purchases.php

Small wording fix.
Template Documentation for widget-cart.php
Spacing for template docs in widget-cart.php

Small spacing fix
Template Documentation for checkout_cart.php
Fixing template docs for checkout_cart.php
Merge pull request #2762 from NikV/master

Template Inline Docs for Templates folder