Added a group change "Prices" - "Markup", based on the "Purchase price".

Added a group change "Prices" - "Markup", based on the "Purchase price". The function takes into account the "Markup" only for those product cards for which the "Purchase price" is specified.

Added the ability to enable email notification about automatic import or update.
Add to cart button icons have been replaced with SVG format.
Added "Purchase price" for varieties.