Loading assets per scene instead of all assets

[JamesTKhan]

Is your feature request related to a problem? Please describe.
Currently Mundus loads all assets on both the Editor and Runtime when loading a project. This is fine for small projects, and even makes scene switching fast, but becomes less practical in large projects with lots of assets.

Describe the solution you'd like
Look into refactoring asset loading to only load what is needed for the current scene to see if its viable.

Additional context
This could be a pretty sizable refactor of the loading system and is not a high priority.