Redundant feature Client vs. Source Overview

[bmario]

"Client Overview" and "Source Overview" are basically the same, but with difficult-to-explain differences and inconsistencies.

While the source overview only lists sources and has a guided config tool for some of them, it also has the raw config button, which funnily doesn't have the big scary popup message. The client overview shows the user a big fat scary message when trying to edit raw JSON configs and an even worse jump-scare when trying to raw edit a source with a matching plugin. However, it doesn't have a mouse-over overlay for the reload config button.

We should merge these two pages into "Client Configuration".

[bmario]

Also, confusingly, dbs are listed in the source overview with a broken guided config tool. (See #59)

[bmario]

Fixed in #61