forceLoadRadius only in worlds connected to 'active' worlds

[leth]

I had an idea for an optimisation:

The behaviour of forceLoadRadius could be modified to only keep the chunks loaded around portal pairs which are connected to a world with at least one online player.

[akrieger]

Makes for a sucky experience if you only have one player online. I'm not sure what the behavior of bukkit is wrt. unloading worlds when there aren't any players in it anyway.

[leth]

Feel free to close this if you don't think it's needed.