*Fix bugs related to tempfile in the case where multiple AbstractDomain are added togather inside another AbstractDomain. Only one and unique tempfile will now be generated (and deleted) in any case (MPI or not).
*Control some verbosity level related to MPI (solver & dirichlet warning)
*Control verbosity level of GMSH

* use with ... as ... structure to avoid errors in case solver diverged
* remove last iteration that can cause solver divergence if dt is very very small (machine precision)

`fenics=2019.1.0` is missing from conda "run requirements".

Use newer `pandoc` release (3.1.12.3) as system dependency to build documentation.

Add missing `pandoc` system dependency to build documentation.

Fix documentation sources path.

Use `sphinx-build` instead of `make`.

Add missing `pandoc` dependency to build documentation.

Update 'pages' CI recipe and `env.yaml`.

Adapt the creation and modification of mesh to the MPI architecture : then mesh can be partitionned and treated separately by multiple cores

Replace `conda activate bvpy` by `source activate bvpy`.