New iava support and numerous other enhancements

[ryran]

Changelog:

• FIX: rhsda.extract_cves_from_input() no longer ignores case when removing duplicates rhsda.extract_cves_from_input() no longer ignores case when removing duplicates #57
• FIX: duplicate CVEs that are present both in stdin and on cmdline are not removed duplicate CVEs that are present both in stdin and on cmdline are not removed #59
• RFE: implement new IAVA support implement new IAVA support #51
• RFE: allow querying multiple IAVAs at once allow querying multiple IAVAs at once #12
• RFE: implement RHSDA_URL environment variable implement RHSDA_URL environment variable #55
• RFE: Rename --extract-stdin to just --stdin Rename --extract-stdin to just --stdin #53
• RFE: display errata release_date field display errata release_date field #52
• RFE: Rename --extract-search (-s) to --extract-cves (-x) Rename --extract-search (-s) to --extract-cves (-x) #54
• RFE: Show more CVE data when performing searches without --extract-cves Show more CVE data when performing searches without --extract-cves #17
• RFE: make --q-xxx options mutually-exclusive with --iava & --stdin & CVE (args) make --q-xxx options mutually-exclusive with --iava & --stdin & CVE (args) #58