Show more accurate time remaining in build and research queues

[fredden]

Fixes #1004

In order to test this, one should enable "No Queue Order" and "No Research Queue Order", and set "Queue Merging" to "Never Merge". When adding two of the same item to the build queue, this change makes the time remaining on the second item more accurate. Also, when two queue items both consume the same resource (eg, University and Bank need Stone), then the item in the queue which would finish second has its time extended to account for the item finishing first using up that resource. This also works for the research queue.

There is an unhanded edge case here: the two queues are independent, so if an item in the research queue and the build queue both require the same resource (eg, Money) then neither item will take this into account, so at least one item will have a misleading time shown.