Update to Beta 0.51

A lot of improvements came to Zombiepede:
- Wave Counter and Health Info for dark skeleton waves in late game
- multiplayer challenges became more difficult
- bug fix: mines were exploding when placing in friendly fire levels
- bug fix: Lich was flying out of the level in the Event Challenge
- Some changes for the greneade launcher updates: for example Speed updates decreased and chances for legendarys to epic
- New Campaign (4: Hardcore) with 5 new difficult levels added
- removed sound spamming of fire golems in late
- added button info for Event challenge
- dark fire golems added to late game
- late game changes to weaker enemies: appear less often for better performance
- new Weapons: Lightninger and Golden Gun
- new Air Strike offer
- made changes to pistol class and general updates: appear more often in early
- Death increases the reroll cost by 1+20% now
- added Blast upgrade to Machine Guns
- Overclock damage increased
- added new Skin
- added two new Profiles: Contract and Master
- some more minor bug fixes...