build: Report missing stuff more nicely for nukes

build: Report missing stuff more nicely for nukes

By switching build_nuke() to sector_can_build(), build_charge().
Changes reporting of missing stuff to be like for ships, planes and
land units:

* Report missing available work, or else missing materials, or else
  missing money instead of materials, or else money, or else work.

* Report what materials are missing instead of how much materials have
  to be there.

* Clean up stray ';' in reporting of missing work.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>