Consecutive import of sample from several Python scripts is affected by previous imports

• Consecutive import of sample from several Python scripts is affected by previous imports [Gennady, Redmine2280]

[edited MP] This is due to the design of using only one single material model for all samples:

Material values will be overwritten if other imported samples have materials with the same name but different values.

Solution: Provide dedicated material list for each sample, completely separated from other samples.