Create additional HTTP endpoints, improve templating

[hi-liang]

Endpoints include:

• Delete a scene
• Create a template scene instance Quick clone a scene

Template refactor:

• Remove @templateScene naming convention, allow any scene to be used as a template
• Deal with TTL exception for @templateScene, whereby expireAt is not set in the mongo document (what actually enforces expiry behavior in mongodb). Perhaps via flags where persist: true, ttl: n are set, but some new flag (retainTTL: true ?) does same bypass of expireAt so every time someone loads the scene from persist (or instantiates a sceneTemplate), the object is kept with a "fresh" TTL

[hi-liang]

Splitting this one one off

Deal with TTL exception for templateScene, whereby expireAt is not set in the mongo document (what actually enforces expiry behavior in mongodb). Perhaps via flags where persist: true, ttl: n are set, but some new flag (retainTTL: true ?) does same bypass of expireAt so every time someone loads the scene from persist (or instantiates a sceneTemplate), the object is kept with a "fresh" TTL

[hi-liang]

Otherwise resolved as of 9643946