Better Sicilian Donjon and krepost

Now we can train spearmen in donjon but we can’t upgrade them. So allow us to upgrade them in the donjon.

I suggest also to allow us to upgrade Serjeant in donjon. Three technology can be put to be researched in the Sicilian donjon : hoarding and squires and arson.

So with this new Sicilian donjon we can upgrade spearmen line and serjeant and research hoarding and squires and arson technology. This Sicilian donjon will be more versatile and a player still build barracks if he want militia line unit and technology (supplies/gambeson) and still build castle if he want trebuchet, conscription and UT.

Also we can allow bulgarian to upgrade konnik in the krepost.