Replace all occurences of operator variable by op_fct to avoid conflict with the c++ operator keyword

PRUVOST Florent authored 6 years ago and Mathieu Faverge committed 6 years ago

    improve user's doc style
    add some explanation about the code structure in the main doxygen
    fix coverage in analysis sonarqube
    add a release job to automatize release publication
    change the cdash server to my.cdash.org which is more recent and reactive than cdash.inria.fr
    fix the version number, dates and authors in headers to prepare the release 0.9.2