Series sales: add validation to ensure that buyer and seller aren't the same#1007

KrivenkoAlexander wants to merge 1 commit intophp-coder:masterphp-coder/mystamps:masterfrom

KrivenkoAlexander:gh503_Series_sales_form_diff_buyer_and_sellerKrivenkoAlexander/mystamps:gh503_Series_sales_form_diff_buyer_and_sellerCopy head branch name to clipboard