In #393 the format of the static user file in --no-db mode changed.
However, the old format loads without error, which has caused
issues for developers with existing user files.
Add an explicit check to ensure the file is not using the old
format. If they are, print a better error message.
In --no-db mode, load passwords from the users file instead of the
connectors file. This allows us to remove the password infos field
from the local connector and stop loading them during connector
registration, a case that was causing panics when using a real
database (see #286).
Fixes#286Closes#340
