Make salting configurable in ConfigurablePasswordProvider

Rather than add a NoSalting subclass, a `salt` field has been
added to CPP (inherited by JdbcPP) but which by default is now
true. An instance of JdbcPasswordProvider with the value set to
fale is available as `jdbcPasswordProvider449` and the full chain
as `chainedPasswordProvider449`.
Add `--no-salt` parameter to `bin/omero db script|password`

In order to allow rolling back to non-salted passwords, the
base CLI commands now allow turning off salting. Between this
and the *449 password providers, it should be able to revert
completely to non-salted logic.