This has the triple bonus effect of a) making a lot of code easier to read, b) reducing Server::getInstance() usages, and c) removing a whole bunch of Server dependencies.
The network and block namespaces are untouched by this commit due to potential for merge conflicts. These should be dealt with separately on master.
* Implemented InventoryEventProcessor, fixes#1986
Event processors can now be registered and unregistered at will. Entity inventory/armor change events are now handled by event processors instead of the inventories themselves, which allows enabling/disabling the calling of these events at will.
This now avoids stupid things happening when initializing inventory contents, since the callers for those events are now registered _after_ the contents are initialized.
