cleanup cleanup

[michael-kenzel]

While working on the plugin system, I had to add some stuff to the Importer and cleaned up a little (mostly inconsistent uses of the world() vs world_ members, I wanted to remove the world() member and make the rest private, but it seems the hls stuff uses it all over the place so I left it public for now).

[Hugobros3]

Please have a look at the development branch and base any changes off it. Of note, I added a Thorin class that effectively holds the world, rather than the world "holding itself" (which makes dumping/diffing two versions of the world impossible)

https://github.com/AnyDSL/thorin/blob/development/src/thorin/world.h#L394

[michael-kenzel]

I revisited these changes. It's now only cleaning up inconsistent uses of the world() vs world_ members.