Refactored operation executor to a command-service-like service.

This includes adding a ScannerOperation annotation to use for all
operations.

AFDP-195
Moved the scanner modules to the service/scanner package.

AFDP-195
Added annotation to operations and altered to be more command-like.

AFDP-195
Changed scanners to use the new scanner operation service API.

AFDP-195