Return of the Horse!

Big changes in this release! Not using Mounted as Airship anymore; the Cavalry has returned as a proper Mounted unit, and Airships are now marked by the "Airship" unique. Plus, lots of modifications to more closely match the original Empires of the Smoky Skies (thank you, Ravignir!) and some tweaks to match Unciv's 3.15.0 release. Enjoy!