added code from the mpi14 library for parallel mpi communication with a nice wrapper interface

I guess a unit test would be really nice, otherwise this looks good to me.

Yes, I have to implement a test for this. I also think that this would be necessary.

added 23 commits

• ed87e483...71f7f813 - 19 commits from branch master
• cf5ec80a - added code from the mpi14 library for parallel mpi communication with a nice wrapper interface
• d54f912a - added test for mpi wrappers
• 41b36558 - test modified and some problems corrected. Does not yet work perfectly.
• 6b3e5e03 - resolved merge conflict

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added 1 commit

• 7b6e29b2 - removed ibsend and buffers, reimplemented wait_all

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added 1 commit

• 174e174e - again redesigned wait_all and Request::test()

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added 1 commit

• e91cc58f - small change in Request::test()

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added 1 commit

• 6f87bc08 - small change in Request::test()

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added 1 commit

• fccc6b17 - implemented Request::test() in terms of Request::status()

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enabled an automatic merge when the pipeline for fccc6b17 succeeds

aborted the automatic merge because source branch was updated

added 2 commits

• 49debe52 - added empty template parameters for std::plus and std::multiplies
• 696972ac - Merge branch 'feature/mpi_wrapper_library' of...

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enabled an automatic merge when the pipeline for 696972ac succeeds

merged

mentioned in commit 9f35f6d0