Allow current regions to be re-definable.

[gravityfox]

Currently, the only way to change the bounds of regions is to delete and remake it. This is dumb.

There are two things I would like for users to be able to do:

• Redefine regions: basically, they select new points for the bounds and run something like /foxguard modify region <name> redefine to set the new bounds.

• Adjust the bounds of regions: Allow things like expanding in a direction a certain number of blocks in a direction.