Remove array delimiters on Ivy messages

- [ocaml] use quotes for char arrays
- char[] are now treated as 'real' strings
- no more delimiters for other arrays (where space characters should not
  appear)

From #929 

Up to now arrays sent on the Ivy bus had a `|` delimiter and you had e.g. `|1,23,4,5|` and `|f,o,o, ,b,a,r|`.
Now it would be `1,23,4,5` and `"foo bar"`.

Todo:
- [ ] backwards compatibility reading arrays in old format e.g. from old logs
- [ ] update all other progs that read ivy messages with arrays which don't use the OCaml lib (C, python...)