* [bitnami/postgresql-ha] Add documentation for usePasswordFile option
The `postgresql.usePasswordFile` option was previously added to mount
passwords as a volume rather than in environment variables but was not
documented.
* [bitnami/postgresql-ha] Add postgresqlPassword option
When `postgresql.username` is not `postgres`, a new user is created that
only has permissions for the database created with `postgresql.database`
and the `postgres` user does not have a password and cannot be accessed
remotely.
This commit adds the `postgresql.postgresPassword` property that can be
used to specify the password for the `postgres` user when
`postgresql.username` is set to a different user.
Resolves#2470.