This takes the changes from 03b23dd1b6
and applies them to the .theme version as well.
(note: It's *possible* to just go through fish_config in future, but
we do not want to do that right now because that can have issues on
upgrade)
These are simple
var val [val val]
files. Basically the bit in `set -g fish_color_escape 86c1b9` after
the `set -g `. Since we're not going to `source` them, however,
arbitrary code and expansions are unsupported.
Also comments and such don't currently work.
This allows them to be easily readable both from webconfig (next
commit) and the shell (later).