1. A non-transitory computer readable medium encoded with program instructions for automatically generating building system application solutions by: verifying an application definition with a system design verifier configured to receive markup language files corresponding to the application definition that identify HVAC components for a building system; delivering the verified application definition from the system design verifier to a system design converter; converting the verified application definition from the system design verifier into a building system application solution installable in a controller of the HVAC components of the building system with the system design converter, the building system application solution including computer statements, wherein the computer statements are executable on a processor of the controller to implement the building system application solution that corresponds to the application definition; providing data from computer tools to the system design converter via a computer tool interface for incorporation within the computer statements; and utilizing an external program module interface coupled to the system design converter to provide modular computer program components to the system design converter for incorporation within the computer statements that are executable on the processor to implement the building system application solution; wherein the computer tool interface and the external program module interface convert statements from the system design converter that are in a common tool interface format, or a common external program interface format.