Change "business system" references back to "business application"

The CIO Council has an [Application Rationalization Playbook](https://www.cio.gov/assets/files/Application-Rationalization-Playbook.pdf) which provides a definition of an application (page 4): "A software program used directly or indirectly to support the program office in delivering on a business or mission function; includes mobile applications."

Prior to this, we never had a concrete, standardized definition of "application" that wasn't overly vague. Reverting to "application" will require us to:
- [ ] Change references to "business system" back to "business application"
- [ ] Update any data dictionary or glossary to present the definition of "application" that the CIO Council's Application Rationalization Playbook has defined.