CG.hpp file

Physics configurations for scalar transport using continuous Galerkin.

General requirements on CGTransport Physics policy classes:

Must define the static function type(), returning the enum value of the policy option. Example:
```
static ctr::PhysicsType type() noexcept {
  return ctr::PhysicsType::ADVECTION;
}
```
which returns the enum value of the option from the underlying option class, collecting all possible options for Physics policies.
Must define the function diffusionRhs(), adding diffusion terms to the right hand side.
Must define the function diffusion_dt(), computing the minumum time step size based on the diffusion term.

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