Decouple color theme and separator theme?

[MaxVerevkin]

One might want to match different separators with different color schemes, or vice versa. Of course it's possible to just override the separator part of the theme, but you have to copy-paste the utf8 codes.

Instead, we can provide a set of separators. Right now I can think of "native" and a few different "powerline" variants.

Any thoughts?

[GladOSkar]

I think the override is enough. You can also put the literal char in there instead of the unicode escape sequence.

[feschber]

I feel like since the default separator is always the powerline left arrow thing it would make sense to just remove that from themes entirely and make it a separate configuration option.