Updating SED-ML export to Level 1 Version 4

[LukasBuecherl]

The xmlns attribute declares the namespace of the SED-ML document. In the current export it looks like this:

<sedML xmlns="http://sed-ml.org/sed-ml/level1/version2" xmlns:math="http://www.w3.org/1998/Math/MathML" level="1" version="2" >

To work with BioSimulators SED-ML Level 1 Version 3 or higher is required. That means it needs to also define the SBML namespace and look like this:

<sedML xmlns="http://sed-ml.org/sed-ml/level1/version2" xmlns:math="http://www.w3.org/1998/Math/MathML" level="1" version="2" xmlns:sbml="http://www.sbml.org/sbml/level3/version2/core">

More information can be found here:

https://docs.biosimulations.org/concepts/conventions/simulation-experiments/