feat: structure object to ASE structure objects adapter

[sbillinge]

Problem

we would like adapters between diffpy.structure structure objects and ASE structure objects

Proposed solution

1. figure out an the ASE structure objects that map onto diffpy.structure objects
2. write adapters that do diffpy -> ase and vice versa

[TingwenZhang]

I can attempt on this issue. However, this issue may take me a month. Is there a deadline on this issue?

[sbillinge]

@TingwenZhang I suggest that you work on one or two of the other issues first to practice the workflow, then we can switch to this one (which is the main event and can take longer). we have a particular workflow where we discuss first behavior, then design, then tests then the code.

[TingwenZhang]

Got it.