add option to read in non-parallel coreas sims in sim2root

[jelenakhlr]

Currently, we can only read in parallel sims. If we try to read single runs, this happens:

Traceback (most recent call last):
File "/sps/grand/hoshima/grand/sim2root/CoREASRawRoot/CoreasToRawROOT.py", line 511, in
CoreasToRawRoot(file, simID)
File "/sps/grand/hoshima/grand/sim2root/CoREASRawRoot/CoreasToRawROOT.py", line 180, in CoreasToRawRoot
parallel = read_list_of_params(inp_input, "PARALLEL") # COREAS-only
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/sps/grand/hoshima/grand/sim2root/CoREASRawRoot/CorsikaInfoFuncs.py", line 70, in read_list_of_params
return list
^^^^
UnboundLocalError: cannot access local variable 'list' where it is not associated with a value