Remove developers view

Let's face it, it's not our best feature:

• Currently, it looks like this:

We used thegamesdb legacy API, and it's not available anymore. The new API has pretty strict rate limit, and while there's !170 (closed), it's currently blocked by a bug in grilo-plugins.

• The data that was there before wasn't very reliable:

There are a lot of duplicates + developers and publishers are mashed up together. With this, trying to browse games using this view turns into a guess game: where can this particular game be.

So, let's just remove it and simplify the code.