[Lammps] Include concept of group in pyiron

[samwaseda]

I would like to suggest to include the concept of group inside pyiron, by allowing the user to have a tag like group in structure.arrays (which is an ASE attribute), which can look like:

structure.arrays["group_A"] = [0, 0, 1, 1, 1, 1, 0, 0]  # maybe has to be numpy array
structure.arrays["group_B"] = [1, 0, 0, 1, 1, 2, 0, 0]  # maybe has to be numpy array

where the numbers 0 and 1 refer to the group ids. This should be translated inside the Lammps script into

group A_0 id 1 2 7 8
group A_1 id 3 4 5 6
group B_0 id 2 3 7 8
group B_1 id 1 4 5
group B_2 id 6