OF-460 + OF-830: Persist log.debug.enabled; LDAP roster group sharing fix

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.

Also includes a fix for OF-830 to properly handle JID-escaping when using LDAP for users and groups.