[dataimport] turn eids_seq_{start,range} into class attributes Only the master-mode store will actually use eids_seq_start to reset the eid sequence.

usr/bin/cubicweb-ctl usr/bin/
usr/lib/python2*/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl