Improving multi-valued restruct in @funcheb class.
Improving multi-valued restruct in @funcheb class.

Restrict now accepts an array of break points, and can restrcit
multivalued functions.

The output is now an array of funcheb objects, which are not
simplified after they are restricted.

asgeirbirkis/chebfun,alshedivat/chebfun,ilovejs/chebfun