Drop Gunyard cost to 2000 (from 2300); reduce workertime.

Reduced workertime is a slight nerf, but it makes it easier to manage
in the early game. The workertime goes up to 50 after an upgrade, like
vehicles.
Drop zero-in time to 10 seconds; fix 'wait' exploit.

This prevents howitzers/mortars from maintaining (or gaining)
zeroed-in state if they cease firing for more than 8 seconds.

Minor cleanup.
Approximately 50% bump in howitzer firing arcs.

Howitzers are extremely tricky to use for field support;
they typically only find success shelling bases. I'm hopeful that
this (in combination with the reduced zero-in time) will make them
more viable as a tool for dealing with enemy forces.