Implement tank with particles with pore diffusion

[schmoelder]

A tank with particles with pore diffusion is required e.g. for fluidized bed or batch uptake, where the volume of the unit changes and pore diffusion plays an important role (in contrast to current CSTR implementation)

todo

• update interface
• add particle module
• remove functions supporting the old interface, e.g. replicateFieldDataDouble

[jbreue16]

An implementation of this should update the CSTR interface to confirm to the generalized unit interface
Also, we should keep the volume variable, but make it truly optional ie no independent state when constant volume is used