Added spawn_system.lua to create a simple SpawnSystem and created a test factory function in SpawnSystem's constructor.

fixes #40 
fixes #59 

Merge pull request #3 from Revolutionary-Games/master

Syncing

Added spawn_system.lua to create a simple SpawnSystem and created a test factory function in SpawnSystem's constructor.

Added a newline to the end of spawn_system.lua

Made a few fixes to spawn_system.lua and moved the test function to setup.lua.

Changed the spawning algorithm. It should now be good for all stationary entities.

Randomized the orientation of spawned emitters

Fixed issue with local/global variables and unhelpful variable names, and changed the spawning method to utilize the built in functions of Vector3

Merge branch 'master' of https://github.com/Revolutionary-Games/Thrive

Fixed some bugs, changed addSpawnType to use spawnDensity rather than spawnFrequency, and added several comments.

Fixed some bugs, changed addSpawnType to use spawnDensity rather than spawnFrequency, and added several comments.