Change org.conman.iconv API.

Return a function as the module.  If we later need a table based module, we
can slap a metatable with a __call() method in it.  Also, make it

	iconv(to,from)

to follow an assignment-like order.  Also, no :close() method.  Let the GC
handle it.
Added some commentary for org.conman.env.
Added some commentary for org.conman.errno.