cleaned up scripts to subfolders

Assets/Scripts/Upgrades/CollectorUpgrade.cs

Assets/Scripts/Upgrades/CollectorUpgrade.cs.meta

Assets/Scripts/Upgrades/PopulationUpgrade.cs

Assets/Scripts/Upgrades/PopulationUpgrade.cs.meta

Assets/Scripts/Upgrades/ResourceCapacityUpgrade.cs

Assets/Scripts/Upgrades/ResourceCapacityUpgrade.cs.meta

Assets/Scripts/Upgrades/ResourceEfficiencyUpgrade.cs

Assets/Scripts/Upgrades/ResourceEfficiencyUpgrade.cs.meta

Assets/Scripts/Upgrades/RoadUpgrade.cs

Assets/Scripts/Upgrades/RoadUpgrade.cs.meta

Assets/Scripts/Upgrades/Upgrade.cs

Assets/Scripts/Upgrades/Upgrade.cs.meta

Assets/Scripts/Upgrades/UpgradeTargets.cs

Assets/Scripts/Upgrades/UpgradeTargets.cs.meta

Assets/Sprites/Grass.png.meta

Assets/Sprites/Sand.png

Assets/Sprites/Sand.png.meta

Assets/Sprites/bilberry.png.meta

Assets/Sprites/house.png.meta

Assets/Sprites/rock.png.meta