Added support for My Worlds

Signed-off-by: Irmo van den Berge <bergerkiller@gmail.com>

Allows 'myworlds' to be selected as a translator, which then starts using the 'shared world name' of all world inventories as specified by MyWorlds. If per-world inventories are disabled in MyWorlds (useWorldInventories false) this support is disabled and uses per-world split inventories instead. I looked at the MultiInv locator to see how things work and tried to mimic it's functionality. After a lot of hassle with missing dependencies and problems compiling because I didn't have the right SDK installed, I let a server owner (who requested support) test the final product, and he confirmed that everything was working as expected.

If any other changes are needed, let me know.