Upgrade to Entities 1.0

[mbaker3]

At the time of writing Entities 1.0-exp.8 has been released.

For the time being we aren't upgrading Anvil until the API is further locked down and the team gets closer to a final 1.0 release.

While not comprehensive, existing anvil code has been annotated with comments pointing back to this issue number to help with the migration.

Upgrade Steps:

• Upgrade package and get anvil compiling again
• Review all references to this issue in code comments and adapt logic as necessary.
• Run main features and profile to ensure they still perform as expected
  • TaskSystem
  • Multi-World PlayerLoop optimization
  • ManagedReference
  • Burstable Logging
• Update Readme

[jkeon]

Due to #301, this task is now just going through the code base to review all references to this issue and planning that work accordingly.