[CB-4345] Added warning message for when signing keys are not installed

- Added check for bbidtoken.csk
- Added information to link old signing keys to the blackberry id token
- changed check_reqs-utils into signing-utils
- Migrated and added unit tests for signing-utils.js
- switched warning message for when author.p12 DNE to when barsigner.db DNE

Reviewed by Bryan Higgins <bhiggins@blackberry.com>
Tested by Daniel Audino <daudino@blackberry.com>