allow to define pre configured shapes on a board with supplied fen

[eronnen]

When configuring a new board with predefined shapes in config.drawable.shapes while also supplying an initial FEN, it ignores the given shapes

[ornicar]

I don't think that's the way to solve it, as we do want to clear the previous shapes when the FEN changes.

[eronnen]

what about adding initialShapes property that will be cleared after the first configure?

[ornicar]

That doesn't sound ideal tbh

[ornicar]

@eronnen v8.3.7 should work as expected