Update interface

[jbreue16]

This is a meta issue to track all the interface changes we want to have for v6

• Improve parameter interface #284
• Update Parameter Sensitivity Interface #126
• Improved reactions interface #77
• Unify flowrate / velocity interface #381
• https://github.com/cadet/CADET-Specification/issues/3
• https://github.com/cadet/CADET-Specification/issues/4
• https://github.com/cadet/CADET-Specification/issues/5