Add support for .sci itervar parameter

[psoftware]

Since Omnet 5.2 version it's no more possible to import vector data generated by iterated experiments. The error is caused by a new .sci parameter type called "itervar" that causes the following error on loadDataset() call: Error in callLoadDataset: missing fields from block, file [...]

From the Omnet 5.2 changelog

Save iteration variables separately from run attributes ("itervar" lines). NOTE: This changes result file format!

This code should mantain the compatibility with the older .sci file versions.