UX updates

• Add item option to remove the padding from images dropped on a zone.
• Add option to show zone border when dragging an item.
• Hides text when a draggable item is placed in a target zone and frontend wait for LMS response, this is done since the size of the item increases when the spinner is visible.
• Change containers and CSS classes to match those from the edx-platform. The problem div now contains the drag container, buttons, and feedback, CSS classes from submit button; submit an answer and action buttons were also changed.
• Improve feedback styles, now only icons show color related to feedback, and text color remains the same also each feedback line doesn't show borders.