Create example data for MaterialProcessing Subclasses

[anastasiyaprymolenna]

A running issue until all MaterialProcessing Subclasses have an example data set committed for them:

• [x] SubsamplingProcess
• [x] MixingProcess
• [x] FiltrationProcess
• [x] PhaseSeparationProcess
• [ ] AcidificationProcess
• [ ] AnalyteStorage
• [x] ExtractionProcess
• [ ] ReactionActivity
• [ ] SievingProcess
• [ ] SampleDrying
• [ ] DerivatizationProcess
• [ ] ChemicalReactionProcess
• [ ] PhMeasuringProcess
• [ ] DissolvingProcess