[Search] Small improvement in the layout

[albertoblaz]

We are using tabs for switching between streams and users, which is a nice pattern in my opinion. But depending on which element we want to search for, we should display different kinds of content on the right side of the window (if we search for users, it does not have too much sense to keep displaying a huge map or a huge graph, I think).

Thus, this tabs should be a bit on top of the content frame and at the same level as the search bar. Another awesome alternative is the dropdown used by GitHub which allows users to search content either in the current repo they are seeing or in all repos.

Below, we can put other stuff like the sorting, the filters, the list of streams and the map-graph panel on the right.