Make downloadable product dropdown ajaxy, as per #4211
escape download handler URLs
esc_url_raw to readfile home_url()
Fixed several @return void clauses. There are more. No code changes in this commit, only PhpDocs

Closes #4216
Explicit currency for order prices

Set the currency for the order prices to be the order's currency instead
of the shop's currency. When these are different, the order emails are
misleading.

Related to https://github.com/woothemes/woocommerce/pull/4143
Clear selection after adding download permissions
Move all download permissions inline js to meta-boxes.js
Merge pull request #4215 from scottbasgaard/master

"Order again" doesn't work. Proposed pass at fix.
Merge pull request #4224 from mihaigrigori/master

Explicit currency for order prices
Merge pull request #4213 from kloon/fix_optimize_downloadable_products_dropdown

Make downloadable product dropdown ajaxy, as per #4211
Minify #4213
Fix default status of variation fields Closes #4205
Grammar of no products found message Closes #4217
Contact first and last name and query them when searching Closes #4174
Isset rather than empty, so states work when allowed countries are set. Closes #4223
Humanize order number/status string Closes #4225
Check for valid post type/products when setting up data
Made error counts work with new notices api Closes #4201
PhpDocs
typo