[wsgi] add the simplest possible wsgi (debug) server
This server is able to:
* serve on a given port using the stdlib SimpleHTTPServer
* run looping tasks
Closes #3005509.
usr/lib/PY_VERSION/*-packages/cubicweb/entities/
usr/lib/PY_VERSION/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/PY_VERSION/*-packages/cubicweb/*.py