Make all submodules agnostic to the state vector order

[jbreue16]

As per discussion in #183 and the #state-seminar-retreat/7, in view of future CADET-Core development, we should make all submodules (convection dispersion operator, binding, reaction, etc) agnostic to the structure of the state vector.
Thats already the case for the convection dispersion operator where we simply pass a stride (two strides in 2D) which defines the stride to the next relevant element.
The binding module however (e.g.) is built on the assumption that all components and bound states are stored continuously.

We can solve this by e.g. passing the strides or a view object (as it is constructed in the DG convection dispersion operator).

For your notice, @schmoelder @AntoniaBerger