WIP: YAC-coupling integration in Elmer (colouring and mpi_handshake)

[BenjaminRodenberg]

The goal of this PR is to prepare the branch yac-coupling for the integration into devel:

• I integrated the mpi_handshake feature (needed by YAC and XIOS) with the colouring scheme in order to avoid conflicts between the two schemes and avoid a degradation.
• I added additional checks to make sure the provided dependencies YAC and/or XIOS are compatible and Elmer is initialized correctly.

Note: Currently, a Windows test is failing. I'm investigating and hopefully fixing this issue in #691

[BenjaminRodenberg]

Note that the Windows tests are still failing. I would suggest to move this topic to another PR if it is a larger issue.

[raback]

The Windows tests seem to be failing but does not seem to be too severe. The first one fails tests "Contact" and "Shell_with_Solid_Beam_Eigen". Upon running again both pass. The 2nd one with external dependencies only fails "Contact" and passes that on rerun. The "Contact" test has shown this kind of instability also before. From the output it would seem that for some reason the "TEST_PASSED" file is not available before its inspection. For some reason it only happens to this test. I will have a look what could make that case so special....

[BenjaminRodenberg]

Thank you for looking into this @raback ! So I understand we do not have to worry about the Windows tests here and can proceed?

What's still missing from my perspective in this PR are a few (manual and maybe even automated) tests. I would like to make sure this change does not introduce a regression if XIOS is used without YAC.

Next steps:

• Testing
• Merge WIP: YAC-coupling integration in Elmer (colouring and mpi_handshake) #682 into yac-coupling
• Create a PR based on yac-coupling with the goal to merge into devel

[BenjaminRodenberg]

I'm a bit unsure about whether we agreed to keep elmer_grid.{c,h} or not. Rest is from my perspective good to go.

Still needs some manual testing. I would suggest to add automated testing at a later point in time and get this feature merged.