azure pipelines

[Thomas-Ulrich]

Add azure-pipelines

• azure-pipelines-template.yml build the application and run the test (it basically does the same as the .travis.yml file, but faster).
• azure-pipelines-clang-format.yml verify that the src, app, and test are formated accorded to clang-format-11. (it is copied and adapted from SeisSol)

None of the tests currently pass, because:

• a few files are not clang-formatted https://tulrich.visualstudio.com/thomasulrich/_build/results?buildId=55&view=logs&j=011e1ec8-6569-5e69-4f06-baf193d1351e&t=6fe8753d-6a09-5e1d-8a3c-02026d6aed54
• the doctest.h is too old

  [ 55%] Building CXX object test/CMakeFiles/test-runner.dir/main.cpp.o
  In file included from /home/vsts/work/1/s/test/main.cpp:2:
  /home/vsts/work/1/s/test/../external/doctest.h:4036:47: error: size of array ‘altStackMem’ is not an integral constant-expression
  4036 |         static char             altStackMem[4 * SIGSTKSZ];
    |                                               ^
  make[2]: *** [test/CMakeFiles/test-runner.dir/build.make:76: test/CMakeFiles/test-runner.dir/main.cpp.o] Error 1
  make[1]: *** [CMakeFiles/Makefile2:1643: test/CMakeFiles/test-runner.dir/all] Error 2

  https://tulrich.visualstudio.com/thomasulrich/_build/results?buildId=55&view=logs&j=7f33e5bd-7764-5d8a-ba2e-506e078b9c3f&t=4dcf5c97-b0e1-5f3b-ee15-0b0e2a3ffb0c

These 2 problems are addressed by separed PR>