Update reference docs for 0.6 release

[teh-cmc]

Wait for things to stabilize first, there's a lot in flux at the moment.

• Rust: Session doesn't exist anymore, see RecordingStream
• Rust & Python: batch environment variables
• Python: init/set_active_recording is mandatory + introduction of individual recording handles
  • and... huh... more
• Blueprints
• The new transform stuff
• Update primitive docs page
  • Draw order

[teh-cmc]

We will intentionally leave blueprints out of 0.6.0 so, ticking that one out.