Challenge interface improvement

• Adding a menu, on main map, to select challenge level
  
• Challenge levels unlock is more obvious and what challenge/reward bring is more clear
  

Upgrades menus improvement

• In upgrades menus, adding base stats ans bonus stats for each plant
  
• Bar graphs come with these statistiques, to get a clear view and scale value
  
• Special skills get this new system too
  
• Bugs on Skinner upgrade panel got fixed