Fix [download_discounts] invalid argument warning.

An invalid argument supplied warning is thrown when there are no
discounts.
Fix empty [download_discounts] invalid argument warning.
fix typos
fix another typo
Merge pull request #1251 from sumobi/master

Fix typos
Simplfiy edd_checkout_button_purchase
Change "Purchase" to "Download" on Free Purchases
slight modification to match new github code
removed double ternary
Add filter for $templates_dir variable

Added a simple filter (`edd_templates_dir`) to give themes the option of setting their own template directory.
Add fallback for item_number
Add Billing Details to top of billing fields
Fix typo
Fix problem with cart fees over writing cart items in PayPal
Helper function to get template directory name.
Moving edd_get_theme_template_dir_name() to template-functions.php
Added edd_get_theme_template_dir_name() function
Allow tax rates to be country-wide. #1260
Merge branch 'master' of github.com:easydigitaldownloads/Easy-Digital-Downloads
added two new actions to checkout template