Nether Islands 1:1 with Overworld Islands

[Mohron]

Requested on Sponge Forums:
https://forums.spongepowered.org/t/skyclaims-skyclaims-is-an-island-plugin-that-integrates-with-griefprevention/16861/55?u=mohron

Add automatic nether islands that are placed 1:1 with their overworld counterparts.

[ronaldburns]

Portals take people to other islands currently, if you could have that changed, too.