Merge branch 'issue/flag_ndebug' into 'master'
changed DEBUG to NOT NDEBUG and removed separate debug target from cmake replaced all occurences of preprocessor directives `#if DEBUG != 0` or similar lines by `#ifndef NDEBUG` See merge request !7
changed DEBUG to NOT NDEBUG and removed separate debug target from cmake replaced all occurences of preprocessor directives `#if DEBUG != 0` or similar lines by `#ifndef NDEBUG` See merge request !7