[repository api] definitly kill usage of word 'pool' to refer to connections set used by a session
Also document session's data storage and some other internals.
Hopefuly things will get clearer.
Closes #1684860: vocabulary confusion in repository code: notion of 'pool'
from os.path import join
from cubicweb.toolsutils import create_dir
option_renamed('pyro-application-id', 'pyro-instance-id')
create_dir(join(config.appdatahome, 'backup'))