Fixed some PreventRoomOverlap issues

[Sooslick]

Fixed some issues and false-negatives in PreventRoomOverlap function:

1. Added swapping min/max in CalculateRoomExtents function before adjusting size (causing room extents stretch instead of shrink);
2. Moved CalculateRoomExtents from CreateRoom function to CreateMap to calculate initial extents correctly;
3. Fixed misleading "replaced room successfully" message for the case where rooms hadn't been replaced at all.