* Add missing header

* use std::is_constructible

- don't insert checkpoints at current time
- warn when dt set to 0 and not finished

Added some hints to explain that the shallow water Riemann problem works in
2D only. The exact Riemann solver is 1D only and the problem is rotated.
The scvf.area() is given in m.

Add the units of the water flux and momentum fluxes in the documentation.

Kilian Weishaupt authored Jul 07, 2020 and Ned Coltman committed Aug 28, 2020

* use std::clamp
* clean up docu
* clean up includes

Melanie Lipp authored Jun 26, 2020 and Kilian Weishaupt committed Aug 26, 2020

In advective flux terms, there sometimes exists a corner velocity in a non-dof
position, in which a velocity is needed. This commit aims at using this existing
velocity instead of doing upwinding.

Replace calls to deprecated `DUNE_VERSION_NEWER_REV(DUNE_ISTL,2,7,1)`
by `DUNE_VERSION_GT_REV(DUNE_ISTL,2,7,0)` which also reads better than
the `GTE` version, as Dune 2.7.1 hasn't been released yet. Fix the
call to `DUNE_VERSION_GT(DUNE_ISTL,2,7)` in the solver factory
backend which would break things in case of a 2.7.1 release. Adapt
the corresponding changelog entry.