Fixed shadow realm crash + improvements

Added option "ShowRealmInfo" to spam the console with information about
realms in pol.cfg

Added number of offline mobiles and multis to the information from
polsys::Realms()

Added new method ListOfflineMobilesInRealm() in uo.em.

Encapsulated the Realm counts to be sure no one's changing them from the
outside.

Added missing core-changes entry ;)