[SWG] Simple Waystones Groups

[1.1.1] - Rename command and same-name fix

• /swg rename <old_name> <new_name>: Admins can rename server groups. Fails with an error if the new name is empty, identical to the current name, or already used by another server group.
• Bug fix — same name for server group and player group: If a server group and your own group had the same name, the mod treated both as the server group (your group disappeared from "My groups", showed in light blue, and showed the server group’s waystones). Selection is now stored as server:Name or player:Name, so both appear separately in the group selection and the correct one is used.