Improve styling for Drag & Drop interaction in Content Scheduler:

• Change background-color for ez-schedule__active-item in order to provide a better readability;
• Add darker background to the drag & drop area, in order to clearly differentiate for the user which blocks are input boxes (like "name" or "limit") and which one are drag-able blocks;
• Add box-shadow to ez-schedule__active-item for its normal state;
• Add a different box-shadow when active-item is hovered over;
• Review font-size of active-item;
• Review size and color for drag icon;
• Review empty states for Active and Queue lists.