ASE objects serialization should be done via JSON not via pickle

[blokhin]

metis-backend/i_structures/struct_utils.py

Lines 455 to 460 in 985a0d8

	def ase_serialize(ase_obj):
	return base64.b64encode(pickle.dumps(ase_obj, protocol=4)).decode("ascii")
	def ase_unserialize(string):
	return pickle.loads(base64.b64decode(string))

[blokhin]

@alinzh please, let’s revisit this