Implement synopsis for help output

Print all the options into the synopsis, for all the output formats
(console, man pages, and HTML).  Formatting is not the nicest possible,
but surely better than what it was (in wman.cpp, the synopsis is only
printed into the man pages, with no wrapping whatsoever).

Part of #969.

Change-Id: Ic09ac91b3d5b5e2d42d41b83935d54c894eb8e97