Storage Facade Iteration 3

[z-arnott]

This will build on the work in issue #21

Iteration 3 will provide:

• Reading vulnerabilities sorted by: risk, cvss severity
• Reading packages sorted by: cons. risk, highest risk, name
• Pagination
• Reading vulnerabilities filtered by: risk, cvss severity
• Reading packages filtered by: cons. risk, highest risk, name
• Purging database by sessionID

[z-arnott]

Add new table for system info: Columns: session_id, system_risk, total_packages, total_cves, high_risk_cves, high_severity_cves