Install update

correction of the install script

migration to alembic

fix alembic bug regarding schema handling
```
gupinot@par-lap04:~/dev/navitia$ if ! sudo -u postgres psql -l | grep -q "^ toto"; then echo true; else echo false; fi
true
gupinot@par-lap04:~/dev/navitia$ if ! sudo -u postgres psql -l | grep -q "^ bretagne"; then echo true; else echo false; fi
false
gupinot@par-lap04:~/dev/navitia$
```

Works here, what's your problem with it?