Revised warehouse level system

I have revised the way the warehouse level affects the warehouse size. Now every level your warehouse size will increase 10% from the base size, and not from the current size as it used to be. This will be more clear to use. Also the level will now start at 0 instead of level 1. So for all you players out there, you just gained a free upgrade of 10% ;).

The price and maximum of the upgrade remained the same (2500XP, Level 10). So you can go to 200% warehouse size, which is 1000 CBM per warehouse.