Add the ability to word-wrap or limit line length

[lquerel]

We should be able to define the maximum line length for comments, for example. Several approaches are possible:

1. Add a word_wrap filter that would take a maximum number of characters per line as a parameter.
2. Add an optional parameter to the existing indent filter to specify a maximum number of characters per line, accounting for indentation.
3. Add a configuration option in the comment_formats section to specify the preferred maximum line length for comments, per language.

These options are not mutually exclusive. Personally, I would be inclined to start with 2 and 3.