Resolve "Implement a simulation object for transport: TransportSimulation."

What does this MR do?

Merge request that gathers !88 (closed) !87 (merged) !64 (merged) and implements a class for transport based on #94 (closed):

This MR does is not meant to fully implement a transport solver, it is to set up the framework for coming work.

• The current local operator implements a finite volume scheme. However, it cannot work yet natively with DORiE due to the discontinuity of the gradients delivered by DG, this will be solved in #62 (closed).
• Although the SimulationTransport implements the methods step() and run() as is stated on the simulation base interface, it cannot be run without the water flux and water content grid functions. Since these grid functions depend on the time, SimulationTransport has to be coupled with the RichardsSimulation object (see #101 (closed)).

This includes a unit test for a dummy simulation with constant flux \mathbf{j}_w=5.55\times10^{-6} and constant water content \theta = 1 (clearly not from Richards equation).

Notice that I added the xml file of parameters for transport but (intentionally) is not included in the DORiE documentation yet.

Is there something that needs to be double checked?

Can this MR be accepted?

• !87 (merged) accepted
• !64 (merged) accepted
• Implemented
• Added unit test
• Pipeline passing
• Documented in doxygen
• Added entry to CHANGELOG.md

No need for documentation in Sphinx yet.

Related issues

Closes #98 (closed)