I'm completely lost in UnitPanel.lua 
Well, maybe I shouldn't have taken civUP as an example, as there seems to be more than one mod merged in it's files...
Also Alpaca have made a custom mission handler, but I'm not sure if it's still compatible with the latest patch, and I've failed to find a simple example of use (or even a thread about it...)
So anyone could point me to a simple mod adding one action to units ?

Well, maybe I shouldn't have taken civUP as an example, as there seems to be more than one mod merged in it's files...
Also Alpaca have made a custom mission handler, but I'm not sure if it's still compatible with the latest patch, and I've failed to find a simple example of use (or even a thread about it...)
So anyone could point me to a simple mod adding one action to units ?