Object data API

[ElusiveMori]

Implement a Lua API for manipulating object data at compiletime. Initial version must have these features:

• Reading stock object data (embedded into Ceres)
• Reading custom object data (object files only) from the map
• Automatically reading and merging all available object data in the default build-script
• Writing object data back into the map
• Object writer should automatically discard unmodified objects and fields to preserve space

[ElusiveMori]

Mostly implemented. Unmodified object data checking is not implemented.