Update 0.9.4

Changes:

• Swarm tower now attack priority targets by default
• Added the ability to go back in time default key "backspace", will go back to begining of wave or previous wave
• Added campaign map Broken mine
• Added campaign map Dump Station
• Improved damage from minigun with 5%

Bug fixes:

• Fixed crash, when loading a newly exported map for the first time
• Fixed crash, when spear did damage on its last frame
• Fixed crash, when clicking npc 2 times in 1 frame
• Fixed crash, when main menu loaded after exiting from map editor
• Fixed crash in main menu that could occure when leaving a map