Fix `//stack -s [num]` shifting the selection to unexpected places. This fix causes `//stack -s [num]` behavior in diagonal directions to be consistent with the behavior in non-diagonal directions, which means that the last stack will be selected.
When loading WorldEdit on a Bukkit server which it does not have an adapter for, a stacktrace is printed to console and WorldEdit does not load. This commit fixes that by registering the BukkitServerInterface before attempting to find a matching adapter.
Pieter12345