Remove vanilla flavour and skin?

The reason I'm thinking doing this is because I don't see any reason to keep it around if the final frontend won't use it at all. Unless there is plans to add switching between Glitch and Vanilla skins in the frontend, I don't see the point and we could save a lot of space, especially with the builds.

Note: The work needed to do this successfully is done. I just need time to think about if I really want to do this or not before I merge it to the develop branch. If you have any feedback about this, let me know.