* turn on bom_tests
* fixed root directories to search
* leftovers fix
* removed requirements from package_BOM.txt; corrected error messages to install via pip
* removed extract_release_version.py from package_BOM.txt, added requirements files to skip
* removed redundant commented line
* mentioned CustomLayersMapping.xml.example in docs
Co-authored-by: Andrei Kochin <andrei.kochin@intel.com>