Add map build height as a world property.

[Fyrecrypts]

It just seems like having the map build height be a property that can be modified would be pretty nice.

[timothyekl]

This is impossible due to vanilla Minecraft and Bukkit limitations. Sorry!

[Rigby90]

Would just like to add... it is impossible in the current state of Minecraft, maybe in 1.9/1.10

Basically the server can set the height to whatever it wants but the client crashes when connecting meaning it's not viable. We'll setup a dev branch with the code all ready I guess and once it finally becomes possible it'll go live.

[IS4Code]

If there is max-build-height in server.properties, why not have it here as well?