Easy editor based assets inspection

[rewin123]

It should be possible to work with handles in component fields through the inspector in a convenient and saveable way. For example, add the ability to edit the parameters of an asset if it is stored in memory, or set the path to an asset saved in a file. This will allow to work directly with such components as StandardMaterial without creating a prefab version of the material. Also, add the ability to create/select assets inside the editor and save them together with the prefab. (This will allow to create StandartMaterial inside the editor and just load textures).