Bug Fixes and Script Changes

Fixed some bugs with the new HUD in relation to the pickups. Altered the
building item spawn script to match the fixes from my other branch.
Pickup Prefabs and Script Linking

Brought in all the misc and car part prefabs. Set up the player item
scripts to interact with the mechanic AI and the car maintenance
scripts.
Win and Lose States, Swap to Car, and Player Damage

Incorporated the basic win/lost states. Made the player switch into the
car when within range and the car is fully repaired. Set up the zombies
and player again so that the player actually takes damage from attacks.