Added support for invokers for medications and conditions.
Removed 'test-stub' from URIs in external_services.js
Changed external_services.js to an example file.
Added external services.js to .gitignore.
Improved error handling in invokers.  Added console debugging statements.
Turned on NodeJS flag to allow self-signed certificates in express.js.  Propagated error handling for conditions to the other supported models in their respective invokers.
Added index retrieval from backend system if information not cached.
Added debug logging capability.  Added debug statements.
Fixed bug in header parsing.