Gold fluctuates up and down during construction

[scottanderson]

Players can spam more construction buildings than they can actually afford to build.

When a construction finishes, gold is refunded and then re-deducted. During this period, the player can create additional construction buildings.

Instead of deducting, returning, and then deducting the gold again, we should remove the refund and second deduction, so that the player just pay gold once when ordering construction.

[VariableVince]

The proposed fix will also change the "attacker is charged for or gets money back from conquered (in construction) building" thing. Which may or may not be something that's in there for a reason, and can affect gameplay.