Release v2.9.21

v2.9.21 -> September 24, 2019

• fix* If state is not found for a country in store settings, remove the state field on reload
• fix* Only show vendor's own uploaded media to a vendor.
• fix* Add required attribute for various input field in dokan_post_input_box function.
• fix* Calculate commission for item by quantity when the commission is set to flat.
• Tweak* Introduce Dokan_Commission class to calculate admin and vendor's commission.
• Tweak* Remove unnecessary placeholder in admin commission field.