Wrap on soft-hyphens

[mgeisler]

It could be useful if we could wrap text on explicit soft-hyphens, U+00AD. In my limited testing, soft-hyphens are shown as spaces in a terminal (I tested with Gnome Terminal). We should therefore remove all soft-hyphens except for those used to break lines. So

A text with ex\u{ad}pli\u{ad}cit soft-hyp\u{ad}hens

will be wrapped as

A test with expli-
cit soft-hyphens

The soft-hyphens are gone, except for the one that got turned into a normal hyphen.

[mgeisler]

This should be possible after #221 has landed.