Add window event validator for Grid Toggle

Revisiting this - maybe would be easier and better to add a context variable for the tab, something like: _TabInfo_GridMode Y/N

Regards,

Carlos Ruiz

Attaching here two patches:

• IDEMPIERE-2571.patch - implements the event window validator for grid toggle

• IDEMPIERE-2571_POC.patch implements a POC to make the payment window read-only on grid mode as suggested by at https://groups.google.com/d/msg/idempiere/gnkNXCF3SCo/GRbFqkmP3MoJ

To test the POC you must execute