Allow to filter specific jobs based on commit message
Allow to filter specific jobs based on commit message

By adding the word `ci_filter` to the last commit of a branch, only jobs
that are listed in the commit message via their name will be executed.

ci_filter: [linux_nvcc-10.2_gcc-5_debug, linux_clang-7_release_c++17, windows_nvcc-10.0_cl-2017_debug, macos_xcode-11.1_release]

BenjaminW3/alpaka,BenjaminW3/alpaka