Added informing about unfinished purchase.

Added informing about unfinished purchase. The function is available for sites with paid hosting. You can specify the period after adding an item to the cart to send out the mailing. The setting is located in the tab "Store", "Checkout", "Newsletter about an unfinished order". You can create your own template in the "My Templates" section.

Added "letter template" with a button for payment.
Added the ability to set a limit for entries in child subcategories.
Added a Template for a letter for automatic registration of users when ordering.