Fix grouped products sold individually add-to-cart

The add-to-cart button for products sold individually on a grouped
product page would always lead to the "Please choose a product to
add to your cart" error. This fixes that, and also restores th
'single_add_to_cart_text' filter to the button's text.
Restore single_add_to_cart_button class
Activation/install/welcome
South Africa states are back :)
South Africa has provinces instead of states
Merge pull request #2593 from thenbrent/group-product-fix

Fix  add-to-cart for grouped products which are sold individually
readme for #2593
Fix animation. Closes #2603.
Update chosen, closes #2594
escape when output, not when saved. #2587
Readme #2587