Version 0.3.1 updates

Contents added:

1. Added a new level "city cry".
2. Three kinds of resources (metal, flammable and wastes) can be collected and used to build equipment and fortifications.
3. Up to 5 up-gradable robots can be built to help fight.
4. Can build automatic machine gun turret, automatic howitzer turret, straw-man with the help of blueprint.
5. The fortifications at each intersection can be rebuilt after being destroyed.
6. Recovery bin at the base can restore the player's HP.
7. Added six zombies and a Boss.
8. A new set of UI is used in the new scenario.
9. Added a Telekinesis to pick up props from a distance.
10. Added the energy shield model with function to push approaching zombies. Optimized contents: 1. Optimized the moving effects.. 2. Optimized oil drum explosion effects with more strength. 3.Optimized the animation of zombie walking, being injured and dying ; head being exploded, being blasted, and being hit fly in particular. 4. Optimized the AI of zombies to hit targets with deadliest hate. 5. The store is simplified, easier to operate and clearer to display, but only in the new scene. 6. The backpack is simplified, one-key acquired, but in the new scene. 7. Grenade throwing optimization. 8. Setting bomb optimization. 9. Optimized the energy shield model. 10. Optimized the hands model.