Add asset importation

[norech]

As suggested by CyrusEpion on Reddit, it would be great to be able to import asset.

One possibility would be to use AssetBundles to import models, rigs and animations, it's easier to implement as this behaviour already exists into the game.

Another possibility would be to implement asset importing inside of Scaphandre itself. In a modding perspective, it would be great to simply be able to import assets.

Another problem is where to put mods assets. A thing that could be done is being able to put assets inside a path named Mods/<MyMod>/ directly. It may mean giving up the Mods/<MyMod>.dll file path, maybe for something like this: Mods/<MyMod>/<MyMod>.dll, or this: Mods/<MyMod>/Assembly.dll.