First campaign mission!

I finally managed to pull it of, the first campaign mission is in the game! It took forever because I had a lot to re-program and re-organizing to do as well as a lot of other problems.

Mechanics:

-Added the first campaign mission to the game (Please leave me some feedback!)
-New Boss: Wyvern Slayer (Campaign only)



Balancing:

-Increased the Wyverns base health to 15000 (before it was 10000)
-Spawners increase their health now if difficulty is higher then medium

Bugfixes:

-Trees and rocks could spawn in the air if their was no block below
-Changed the collider of the bridges that falling through them is impossible now
-You did not lose gold when having negative taxes
-When the blacksmith does get destroyed he now resets when building him new
-The blacksmith will reset if he gets stuck at the stockpile