• add #1009 Create sub-grids on the fly,
  by dragging items completely over others (nest) vs partially (push) using new flag GridStackOptions.subGridDynamic=true.
  Thank you [StephanP] for sponsoring it.
  
  See advance Nested
• add - ability to pause drag&drop collision until the user stops moving - see DDDragOpt.pause (used for creating nested grids on the fly based on gesture).
• add #1943 you can now drag sub-grids into other sub-grids