Document that IdRepo now supports StartTLS connections

With OPENAM-3714 the data stores now support StartTLS for secure connections. As part of the work there were changes made to the configuration schema (sunIdentityRepositoryService service):

• the sun-idrepo-ldapv3-config-ssl-enabled property has been removed
• the new property of "sun-idrepo-ldapv3-config-connection-mode" has been introduced with the possible values of "LDAP", "LDAPS", "StartTLS".
  This means that existing ssoadm scripts will need to be updated to use the new configuration attribute.
  Existing configurations are upgraded by the upgrade procedure.