Added setContainer() method for Drag.Move
Drag.Move.setContainer() rewrite suggested by anutron
Added specs for new method setContainer()
Merge: 'pr1137' - new method setContainer()

This allows us to set and change drag container also after Drag.Move constructor call, and multiple times - closes #1137

* pr1137:
  Added specs for new method setContainer()
  Drag.Move.setContainer() rewrite suggested by anutron
  Added setContainer() method for Drag.Move