Add special membranes for species that only pass through to it but not diffuse

Description

The current approach for membranes treatment consists of fully resolving the membrane as stripes between big compartments and resolve a diffusion-reaction system within it as well. This is not very useful when substances pass across the membrane, allowing reactions to happen within extra substances in the membrane but not diffusion within it.

Proposal

Add special compartments that only accept cubes and that will be resolved with a P^0(\mathcal{T}_h) space. This will allow species to cross the membrane without further diffusion on whithin the membrane if diffusion is set to 0.

How to test the implementation?

Set a model that moves an species through a membrane in only one direction, and that no diffusion is seen in the membrane but in the comartments.

Related issues

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