Customizing (a bit) the status line

[acidrums4]

Hearing about #1123 made me realize something (maybe really silly for you) I miss from vim - customizing stuff in the status line.

This is how it currently looks like in several modes:

Though not wanting a status line full of sparkles and stuff, something that I found nice and useful back in those days was that one could make it so each mode had its own (background) color. So what I wish is being able to make possible something like this:

Of course that should work only in active views, where as in inactive views it could look something like this:

[dther]

I decided to give this a try while messing with the UI code, and was surprised to discover that it was completely impossible in the current version of vis. That being said, if you're willing to compile your own vis, I've included a working example for how PR #1180 can be used to implement this!