Add more specific/refined categories

[Malcolmnixon]

Some assets appear to be published under categories which aren't clear, or seem ambiguous. For example:

• Characters, Models, Effects, and Sounds all under the "Misc" category
• Full games under both "Projects" and "Demos"

It might be clearer to introduce more specific asset categories such as:

• 3D/Environments
• 3D/Characters
• 3D/Props
• 2D/Environments
• 2D/Characters
• 2D/Props
• Audio/Ambiance
• Audio/Effects

[Calinou]

This can't be fixed by adding more categories, since each asset can only be under one category. Instead, a tag system should be used. It's already implemented in the asset library rewrite, but there is no ETA for deploying it.