Basically what the title says, make it so the clear production button for factories removes all items in queue except current in production.

If current is only item in queue, remove it.

Motivation

It is the case that often players want to clear queue but keep progress on current unit being built. This makes it so while keeping it easy to support the remove all items case (just issue the command twice)

Proposed fix

Check if #commands > 1 and skip the first removal on the loop by starting the index from 2 instead. Here: https://github.com/badosu/Beyond-All-Reason/blob/badosu%2Frework-gridmenu/luarules/gadgets/cmd_factory_stop_production.lua#L78-L80