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.
Dogfooding on select boxes.
Syntax fix.
Keep name argument for now.
Add filter for template tags description
Merge pull request #1249 from ghost1227/master

Added filter for template tags description
Correct tax display bug on checkout. #1239
Fix error on tax save. #1235
Add Choose to country list and allow all tax rates to be deleted. #1235
Move email template tags function to emails/functions.php. #1249
Added missing textdomain
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.