Added an advanced editor of fields for the Feedback Form.

Added an advanced editor of fields for the Feedback Form. You can create up to 50 fields, with different data types (text fields, strings, file uploads, chachkbox and select elements). Form management is located in the settings, in the "Feedback" tab.

Added new template with demo and quick install.
Added instructions for creating a pop-up block with the contents of the shopping cart.
Updated the style of the Admin Panel and Admin Center for mobile devices.