New housing tier

• New houses for new tier 3.
  
• Previous 3 and 4 tiers are now 4 and 5.
  
• The new tier needs medium Security (more bellow), medium Water, and Mud walls.
  

New production Chain: Leather.

• New Product: Hides and Leather.
  
• New production building: Tannery, where Leather is made from Hides and Salt.
  
• New technology: Tannery.
  

Changes in security

The security level at every Guard Post can now be set to Medium, High or Very High.
Security guards will consume products monthly according to its level.
-Medium: Leather.
-High: Leather + Copper weapons.
-Very High: Leather + Bronze weapons

Save game compatibility: All previous versions are still playable. The Guard post from previous versions will be set to medium security level.

Other changes and fixes:
-Salt production has been increased.
-Fixed: Livestock enclosures not working after hiring workers from zero.
-Fixed: Plazas being built over water.