[repoapi, cwconfig] give a convenience method to get a repository from a config This is a very common need. The private repoapi._get_inmemory_repo becomes config.repository(...)

usr/lib/python2*/*-packages/cubicweb/entities/
usr/lib/python2*/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/python2*/*-packages/cubicweb/*.py