Upgrading Checklist 2.0.0

WIP

Upgrading from older versions to odb 2.0.0

2.0.0 is a rework with minimal API impact. Porting should be relatively easy, unless you use entity factories. If you get stuck hop on gitter for help.

checklist

• Replace ComponentMapper#getSafe with ComponentMapper#get(), which is now safe.
• Replace Entity#edit().deleteEntity() with World.deleteEntity(entity).
• Migrate away from EntityFactories, see #428. Consider using entity deserialization instead.
• Remove usages of PackedComponent and @PackedWeaver. They had no benefit.
• Add public no-arg constructor to all components.
• maven/gradle/ide dependencies: - Remove dependency 'artemis-odb-processor', no longer needed. - Include artemis-odb-serializer if using any serialization.
• Consider impact of : - All systems are first injected, after which all systems are initialized. Previously, each system was injected/initialized at the same time. - Calling BaseSystem#process will now run the system, even if setEnabled(false) has been called. SystemInvocationStrategy now tracks which systems are enabled/disabled.
• Update custom implementations of SystemInvocationStrategy.
  • bag-of-systems now stored as a field, instead of being passed as a parameter to InvocationStrategy::process
  • InvocationStrategy::updateEntityStates must be called before processing the first system.
  • Make SystemInvocationStrategy responsible for skipping disabled systems.

Notable new features

• Odb managed entity references EntityLinkManager, automating cleanup, react on state changes.
• Extend the lifecycle of component types @DelayedComponentRemoval.
• Keep multi-subscription systems cleaner with @AspectDescriptor.
• kryo serializer thanks to piotr-j.