[c-c create] make post-create step optional (closes #2712041)
In this context the "post-create" step refers to the database's creation and
initialization. We want to be able to create a new instance but skip the
database creation (`db-create` and `db-init` commands) in automatic setup.
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/entities/ usr/lib/PY_VERSION/site-packages/cubicweb
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/ext/ usr/lib/PY_VERSION/site-packages/cubicweb
debian/tmp/usr/share/cubicweb/cubes/ usr/share/cubicweb/
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/*.py usr/share/pyshared/cubicweb