0.4.0:
Update to 1.18
Fixes
 - Fix potential nullpointer rendering breaking overlay
 - Fix inconsistency in minecart model
 - Fix memory leak when instance worlds get reset
Technical/API
 - No more MaterialSpec, everything is StructType
 - Move most user facing interfaces to flywheel.api package
 - Refactor InstanceData to have no package private fields
 - Rename many interfaces
 - All materials use the same vertex format: UNLIT_MODEL
 - call #tick and #beginFrame on instance creation
 - Fixes weird delay in object appearance when reloading chunks
 - Add instances when chunks are built for rendering
 - Server worlds are not flywheel worlds