Merge branch 'issue/git_submodules' into 'develop'

added cmake code to automatically update git submodules

See merge request !91
4 jobs for develop in 31 minutes and 39 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #8585
debian:10 clang-6-libcpp-17

00:31:39

passed #8584
debian:10 gcc-8-17

00:20:52

passed #8586
debian:9 gcc-6-14

00:22:21

passed #8587
ubuntu:18.04 clang-6-17

00:29:32