[4.4] Dumbbell lattices

`get_dumbbell_vector`, `Dumbbell_Lattice`, and the dumbbell workflow from https://atomap.org/dumbbell_lattice.html — including the interactive step where the user identifies the dumbbell vector.

Part of #74.

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Plan: [`RELEASE_0_3_0_PLAN.md`](../blob/main/RELEASE_0_3_0_PLAN.md)