Don't mutate ordered dict while iterating it in scripts/generateBoard.py
Don't mutate ordered dict while iterating it in scripts/generateBoard.py

Instead of deleting reference keys immediatelly - which sometimes rises
an exception because ordered dict which is iterated is mutated - mark
them for deletion and do that after the iteration.

jasmin-j/distortos,CezaryGapinski/distortos,DISTORTEC/distortos,DISTORTEC/distortos,CezaryGapinski/distortos,DISTORTEC/distortos,jasmin-j/distortos,CezaryGapinski/distortos,CezaryGapinski/distortos,jasmin-j/distortos,jasmin-j/distortos,jasmin-j/distortos,DISTORTEC/distortos,CezaryGapinski/distortos