Hotfix v0.31.179

Another handful of kilobytes that make Learning Factory better:

• Zeppelins' highlight transparency decreased while they are in mid-air

• Zeppelin shadows transparency decreases while Zeppelins are high from the ground

• Decreased size of all Zeppelins (suggested by Milarky)

• 1 new hidden achievement

• Lots of bug fixes (kudos to Milarky, S'Kleer)