Allow define DropConstraint for CanMoveRule

CanMoveRule only checks if item isn't moved to inside himself, but we need to define dropConstrain for more complex checks.
In Magnolia 5 framework dropConstraint was defined on workbench level and it was used by views and actions, but in Magnolia 6 framework this is defined on view level. That means action/rules doesn't have access to it an we need to define dropConstrain directly in CanMoveRule.

AC:

• Allow specify dropConstrain in CanMoveRuleDefinition