make mpi optional for amuse-framework

[ipelupessy]

this needs to be tested

[ipelupessy]

not sure this is the correct approach..with the current configure it does not matter if MPI with or without mpi4py is installed, AMUSE will be correctly configured and functional for the environment..maybe we should just drop the mpi4py requirement for all packages (and maybe make a seperate package amuse-mpi for this?)..the only reason not to do this is that we also use mpi4py as a sort of check for the presence of MPI...

[ipelupessy]

it would be nice to have amusifier report what MPI functionality the installation has...

[ipelupessy]

now only amuse-framework has the option of being pip installed w/o mpi4py...

[ipelupessy]

if you install non-mpi with mpi available, but w/o mpi4py and add mpi4py later, the MPI channel will work
if you do while mpi is not available, installing mpi4py will not enable MPI channel

[codecov]

Codecov Report

Merging #521 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #521   +/-   ##
=======================================
  Coverage   81.36%   81.36%           
=======================================
  Files         130      130           
  Lines       39359    39359           
=======================================
  Hits        32024    32024           
  Misses       7335     7335

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[ipelupessy]

ok, I don't think we need codecov report here!!

[rieder]

No that seems a bit much...

[ipelupessy]

I think this PR might actually work...

[ipelupessy]

but it is nice that codecov works..I looked at the report and it reports detailed info, can be very handy

[rieder]

yes I think so too. I've now disabled the comments, but it'll still work.

[rieder]

Not related to the changes here, but packages/amuse/pyproject.toml should not have versions hardcoded, ideally...