* Added option for importers to show an Advanced settings dialog
* Created advanced settings dialog for Scene Importer
* Cleaned up importers (remove many old/unused options)
* Added the ability to customize every node, material, mesh and animation individually
* Saving to animations and meshes to files is now a manual process, making it more predictable
* Added the ability for materials to be replaced by external files (or to be made external, up to you).
* When doubleclicking an impoted scene in the filesystem dock, it automatically shows the import settings instead of asking to open it.
WARNING: Lightmap UV unwrap is not working, it needs to be re-made.
