Fix SimpleNetworkWrapper - this is not me modding,
I didn't realize it was broken until Pahimar told me.

Put an example in the docs.
Fix vanilla bug causing integrated server saving from 2 threads concurrently after a crash
Registry: Fix Block-before-ItemBlock allocation when loading 1.6 world saves, more validation
prevent the world from getting saved twice at shutdown
Registry: Crash earlier with conflicting name/object registrations.
Registry: Misc tweaks
Registry: Treat all 1.6 entries as items.