Import Stats Tracking

[jmbarne3]

Enhancements:

• Adds a model for tracking last import time and stats related to the program import.
• Adds logic into the program import for tracking changes, e.g. number of records processed, created, modified, revalidated and invalidated.
• Adds logic to the program and catalog importers to use a default user for auditing purposes. This user is set in the settings_local.py file with the setting IMPORT_USER_ID