* this is in preparation for future support in bevy & for more coherence & practicality
* overhauled metadata tooling
* overhauled most of the operators
* overhauled most of the UI
* all the basics & more work !
* unrelated: also started preping for auto_export operator removal
* removed a lot of obsolete code
* overhauled settings upsert
* added save & load of blenvy common settings
* removed most of the specific uis (mostly auto export)
* moved change detection logic out of auto export (wip)
* added helper to compare setting dicts
* cleaned up some incoherent naming
* stripped auto_export of a lot of its internals (wip)
* main settings ui overhaul: now components & auto export provide their own settings UI function
* added Asset propertygroup & User Assets collections to collections & scenes to store them explicitely
* overhauled UI to make use of this : also means names & paths are editable after the fact
* overhauled testing asset hierarchy scan accordingly
* added expertimental export of bevy_asset_loader compatible asset.ron files per level
* related tweaks & additions
* added correct injection of assets + export path to blueprints
* moved a few common elements to "core" for better reuse
* more tweaks/ experiments with paths handling
* moved & overhauled a few of the blueprint & assets tools
* lots of minor tweaks & changes
* minor tweaks & improvements to assets handling
* renamed a few auto export preferences for more coherence
* "assets" folder is now mandatory again and used by the various sub asset types
* blueprints/levels/materials paths in auto_export are not overwrite their relative values anymore,
but added their "full" variants & changed code using full paths to use those
* added back gltf exporter post export callback, in a cleaner fashion
* changing (wip) the way the various relative folders are auto generated in the folder selection UI
* lots of other minor tweaks & improvements
