Updated Ranch and Xmas scripts

Fixed problems with the cave object placement.

Improved the quality of Xmas tree rewards.
Added world/interior support to some modules

Campfires, HackTraps and static loot spawns now have virtual world and
interior world properties.
Tweaked loot spawn rates
Updated trailers and vehicle trunk sizes

Trailers are now a vehicle flag rather than a category, this allows
trailers to spawn in regular truck spawns.
Removed trailer category
Increased the size of boxes
Updated vehicle spawning code

Improved vehicle placement file (.VPL) parser to better handle different
parameter cases.