Integration tests make target

Integration tests executable using 'make integration_tests'. Clean up CI
a bit.

Change log:
* add integration_tests as a CMake target
* use integration_tests make target in CI
* update README
* CMake command compatible with CentOS7
* CI adjustments
6 jobs for 112-integration-tests-as-a-cmake-target in 13 minutes and 49 seconds (queued for 1 second)
Status Name Job ID Coverage
  Static Analysis
passed Format #5960
docker

00:00:42

passed Lint #5961
docker

00:05:21

 
  Build
passed Documentation #5962
docker

00:02:18

 
  Test
passed Authorisation Disabled #5964
docker

00:01:51

passed Centos7 #5965
docker

00:01:43

passed Default #5963
docker

00:01:53