Add small distinct unit type icons to unit portraits

[historic_bruno]

Could you elaborate on this a bit, what different types are you thinking of?

One thing I can say, there has been some discussion on having consistent background colors on new unit portraits that are being drawn, to distinguish the types (e.g. support / citizen-soldier / warrior / hero).

[rdxi]

I was thinking about making this rock-paper-scissors thing a little bit more recognizable. See screenshots for example.