Outgoing caravans should default to full trades

[Endovior]

Game version
0.2.7

Description
Currently, outgoing trade caravans default to selling 400 items, regardless of prices or capacity, unless the available quantity of the sold good is less than that. Ideally, I'd like them to default to making a full trade.

For example, I currently have two trading partners. One buys metal and sells food. The price they offer is 5 food for every 10 metal. That means my caravan will be coming back emptier than they left, so I can send out a full caravan with 750 metal and get back 375 food. In that situation I'd prefer to send out 750 metal by default.

The other trade partner buys rope and sells metal. The price they offer is 40 metal for every 10 rope. The capacity is the same, but the price difference means that they'll be going out emptier than they return. Also, it doesn't make sense to send out 400 rope when I can get 750 metal back by sending 190 rope (750 / 4 = 187.5; in units of 10, I need to send out 190 to get back a full trade). When trading with them, I'd prefer to send out 190 rope by default.

Determining just what these defaults should be for arbitrary prices would take a bit of calculation, but automatically trading to capacity would be a noticeable QoL improvement for the trading system.

[nroutasuo]

This is a good suggestion, I'll look into implementing it at some point.