Create template/library policies to improve usability

[behnazh-w]

• We need to provide template policies that can be used to detect certain violations with minimal changes (e.g., only requiring to set the software component's PURL) and with no requirement to understand Datalog.
• These policies can also be created as Datalog libraries. Users should be be able to import them easily and build upon them.
• The Datalog relations/library APIs need to be documented on the website.