[server/test] make unittest_migractions.py use new style cubes MigrationTC used old cube layout in cubicweb/server/test/data-migractions/cubes, move them to new style cubes as "cubicweb_<cubename>" in "apphome" (cubicweb/server/test/data-migractions/) which is added to PYTHONPATH by CubicWebTC.

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances