Merge branch 'doc' into 'master'

Doc

- 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

See merge request solverstack/chameleon!147