Build paragraphs, in a bodgy slow way.

Build paragraphs, in a bodgy slow way.

For the moment, I've made a CharIterator that returns each coloured
character of a ColouredString one by one. That's nasty, but easy. I
think more ideally I'd want an iterator that returned contiguous
chunks of a ColouredString according to a filter function passed in
that classifies characters as wanting to be in the same chunk. But
that involves function parameters, so I can try that later.