ZENGINE: Remove implicit cast between integer types
ZENGINE: Standardize naming conventions to fit the rest of the code base
ZENGINE: Clean up includes
ZENGINE: Move utility functions to a cpp file with declarations in a header file
ZENGINE: Remove unused methods from ZEngine class
ZENGINE: Add ActionNode class

This class encases actions that happen over time (timer, animations, etc)
Each frame, the engine calls process() on each active ActionNode
ZENGINE: Implement ActionTimer::execute()
ZENGINE: Create main containers in ScriptManager
ZENGINE: Create utility method to remove duplicate entries from a Common::Array
ZENGINE: Create ScriptManager state handling logic