[blog] add more posts; remove stubs and sample posts

_posts/2018-06-13-arbre.html

_posts/2018-06-13-pla.html

_posts/2018-06-13-pomm.html

_posts/2018-06-13-test.html

_posts/2019-01-16-frama-c-script.md

_posts/2019-02-26-darpa-cgc.md

_posts/2019-06-22-jungle.html

_posts/2019-08-22-welcome-to-jekyll.md

assets/img/blog/darpa.webp

assets/img/blog/measure.webp

assets/img/blog/script.webp