CDAP-538: Ported procedures of the Purchase app to services.

@ParthGandhi The Purchase app has been updated with services instead of procedures, please take a look.
Should these lines be ordered alphabetically? Such as:
```
program_action $app "PurchaseFlow" "flow" $action $host
program_action $app "CatalogLookupService" "service" $action $host
program_action $app "PurchaseHistoryService" "service" $action $host
```

The block above this needs the same treatment...