adding a market room

new file:   assets/textures/shopkeeper.png
modified:   src/entity/EntityManager.java
new file:   src/entity/npc/Shopkeeper.java
modified:   src/entity/player/Player.java
modified:   src/environment/MapGenerator.java
modified:   src/environment/blocks/BatteryReceptacleBlock.java
new file:   src/environment/room/Market.java
modified:   src/event/control/PlayerControl.java
modified:   src/item/Equipment.java
modified:   src/item/weapon/EnergyWeapon.java
modified:   src/item/weapon/LaserRifle.java
modified:   src/item/weapon/Weapon.java
modified:   src/physics/GameBodyType.java
modified:   src/userInterface/inventory/Inventory.java
handling the droping of both keys and batteries

modified:   src/entity/player/Player.java
modified:   src/event/control/PlayerControl.java
adding a zombie in each energy room
a bit of cleaning

modified:   src/entity/LivingEntity.java
modified:   src/entity/player/Player.java
modified:   src/environment/room/EnergyRoom.java