First prototype for Lux potential

[CheukHinHoJerry]

WIP

cc @YangshuaiWang

[cortner]

The idea was not add this as an example to the new repo but rather as a prototype for a new potential. We need to reorganise this into a proper package.

[CheukHinHoJerry]

sorry for misnaming - since the State idea was working gradually on EQM's end we think it is time for us to move all the draft to here and implement it carefully.

I will rename the PR to prevent confusion.

[cortner]

I'm saying don't even commit as examples. Put it directly into a package structure.

It's not the end of the world just pollutes the git history more than is necessary.

[cortner]

Secondly - data files should almost never be in a git repo. We have Artifacts for that.

[CheukHinHoJerry]

Sorry about that, I will also be aware in future development. Could you please advise whether we should create a new PR or clean everything up with a single commit?