New patch (v71)

This one's mainly about tweaking the difficulty to make it a little easier to start with, and fixing a few bugs.

• Get rid of burned out vehicles (for new maps) as it's confusing/frustrating that you can't enter them. Also increased number of vehicles generated on roads so there's more hiding places.
  
• Made pickaxes, shovels and antigen more common
  
• Made ranged weapons a little more accurate and faster to aim
  
• Increased time to fight off a zombie when they grab you, before they get bitten
  
• Made you get a little less tired in melee combat
  
• Made zombies a little more easily distracted by rancid meat, added a hint for that, and fixed some bugs with stealth
  
• Fix for sometimes triggering war with friendlies by swinging a weapon at a dead zombie