Implement weapon 5 level 1

Details:
- Tower with this weapon will freeze enemy in the collision range, and
then kill it directly, by calling removeCollide and killAllien.
After alien gets killed, sometimes the image is not being cleaned up.
*Need to work on this later*.
- Right now, the animation used for this weapon is the 'old' black hole.
but later we will use snow flake instead.
- The weapon is currently assigned to TOWER 4  (not the last tower)

The order of weapon may be changed after we finished all the weapons
implementation, based on how powerful each weapon is (hope that make
sense :D)