Add option to allow for dust when checking outputs

[benthecarman]

This seems standard in most wallet libraries nowadays to give users the option to allow for dust if they know what they are doing.

[guggero]

You mentioned you need this for OP_RETURN outputs. But those should already be exempt by the check here. So I don't really see why this is needed? Or how exactly are you creating the OP_RETURN outputs?

[benthecarman]

If the op return output is over the standard 80 byte limit it is considered dust.

[guggero]

Ah yes. So you'd need a non-standard implementation of a chain backend to propagate such an output in the first place...

[benthecarman]

Yeah I use Libre relay