Alpha 4 hotfix 2

[h3]Changed:[/h3]

• Now there's more chance citizens will buy multiple products in one go
  
• Granary capacity increased to 20k
  

[h3]Fixed:[/h3]

• Citizens did basically nothing on 2-core processors (need confirmation)
  
• Bridges could still make rare inaccessible zones
  
• The game was very productive in creating corrupted saves (need confirmation)
  
• School building was too demanding on terrain flatness