Sort unit lists shown to the user

[lmoureaux]

On top of #2287 - check the second commit.

This patch makes the user interface look more consistent by sorting units in two contexts:

• In the city dialog
• In the unit picker

The sorting logic is an improved version of code formerly used to sort units in the city dialog (but that had been lost for some reasion). It tries to produce a sort order that looks natural and is stable in time. To do so:

• Loaded units are always sorted right after their transport, so one can tell in which transport they are loaded;
• The best defensive units go to the beginning of the list. These tend to stay in cities and not move around too much;
• Tie breaker by unit type and nationality ensure similar units are grouped together;
• Finally, the unit id is used as a last resort.

I tested this logic in a few contexts and it seems to achieve its goal. With respect to the previous sorting function, I removed an order based on unit activities (fortified, fortifying, sentried) because it felt wrong to have a unit move in the list just because I changed its activity.

Closes #1836. See #1838.

[lmoureaux]

The order you show is not what I intended, the planes should come right after the carrier and the defending rifles should be first. This is strange...

I agree that more rows should be shown if possible, but right now I'm not sure how to do that (it's not the same widget as in the unit thing).

[jwrober]

Ok. Loaded units "before" vs "after" is a thing. As long as we are consistent either is ok with me. Maybe sorting still needs some work. I'm also ok with tackling the city dialog scaling to two rows later.

[jwrober]

Everything looks good except for the situation where a ship with loaded units is present in the city. The dialog shows the ship + loaded units first and then best defender.

[lmoureaux]

Ok will check, thanks

[lmoureaux]

Everything looks good except for the situation where a ship with loaded units is present in the city. The dialog shows the ship + loaded units first and then best defender.

I can't reproduce this behavior