OF-460: Persist log.debug.enabled property

Fix settings for debug log so the admin UI setting is retained across
restarts. The system property "log.debug.enabled" may also be used to
manage this setting. If provided via openfire.xml, the property will be
migrated into the DB during startup.
OF-830: Do not use JID-escaping for group names

Fixes roster group sharing when using the LDAP provider for users and
groups, by reverting part of an earlier fix (OF-779).