Added + and - before radius as an optional char

This allows players to perform time based, vote based or donation based commands to increase the map size.
Examples:
1) Player votes, increase the map by 1 block
2) Player joins (more players) increase the map, Player is offline for X days decrease the map
3) Reached donation goal, increase the map
Not sure if this can cause errors if this is the first time you are "setting" the border. will getBorder (borderdata) return null?. If so, best to check if first.