Campaign: Show group number membership in transport menu

[stephenangelico]

Describe the feature you'd like
Show a number on any tank/droid in the transport menu if it is a member of any group

Describe why do you think it is needed
When I play away missions in campaign, I may have multiple truck groups, and obviously multiple combat groups, each with units of common design. When browsing available reinforcements, because the order of units is not sorted by group (I'm not sure what the sort order is - droid age?), sometimes I want to call the remaining members of the group, but I'll inevitably get the wrong droid. (This is particularly a problem for non-combat units as they don't have experience ranks to distinguish them.)

My thinking is to have the group number, if present, to be in the top left of the droid card, basically the same as in the groups menu.