Draft - Make dialogue panel more easily extended.

[esklarski]

I made a few small changes to make extending the dialogue panel easier.

• Use unique name access in dialogue scene
• Add class_name identifier

This allows adding functionality as easy as:

Where I duplicated the default scene, detached the script and added this one and a TextureRect for a portrait.

This produces no functional change in the Orchestrator base as far as a user would be concerned.

[Naros]

Thanks, @esklarski, this change LGTM. Congrats on your first contribution 🎉