Update 0.3.4

This update brings two new enemies and some changes to the spawn system and other misc. fixes 

• New Enemies
  • Small petrol boat that moves fast and shots fast. Can start spawning from the start.
  • Battleship variant that launches large missiles that does massive damage. these missiles can be shot down. Can start spawning after the 5 wave.
• Changes to spawn system includes small value changes and an addition
• The spawn system can now add new enemies into the spawn pool. currently every 5th wave a random enemy gets added
• Sound settings works better now then before 
• Added a small tutorial before starting a game (Already working on a better one)