Create a tree representing an operation
op=Operation(operator,operands,out)
operator symbol (character string)
list of operands (list of "M2SCI tlists")
list of outputs (list of "M2SCI tlists")
an "operation" tlist
This function create a tlist
representing an operation when using M2SCI.
All input parameters values are verified to be compatible with "M2SCI tlists".