X++ in AX7: Forms implementing interface

 This is pretty cool, because:

1. The compiler will validate that the interface is correctly implemented.
2. No longer a need to use reflection, like hasFormMethod(), to determine if it is safe to call the method.
3. No longer a need to downcast to object to invoke the methods. Now cast to the interface:
   
   var sysPackable = myFormRun as SysPackable;
   
   if (sysPackable) 
   {  
       sysPackable.pack();  
   }  

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