Rename Hex Region

[Mochnant]

Currently the ARegion (a hex) name field is used to store the actual multihex "region" name, duplicated in each name field of the "region".

As a companion to NAME CITY <new name>, and to enhance RP potential, add the ability to rename a region: NAME REGION <new name>. It could have the same cost as a CITY rename (3x base) or it could have a custom value in rules.cpp.