Add generic and shared support for OVAL

[pombredanne]

#59 #111 #65 #44 #16 may all somehow use OVAL at some level
It would be great to have a generic support for OVAL XML which rather deeply nested and with several indirection.
Some tools/libs:

• https://github.com/OpenSCAP/OVAL-visualization-as-graph in Python
• https://github.com/quay/goval-parser in Go
• https://github.com/cve-search/VIA4CVE/blob/master/sources/OVAL.py in Python
• https://github.com/cjaymes/pyscap in Python by @cjaymes but this is GPL-licensed... so we would need to ask for some GPL exception or some LGPL to use it here? (See also https://gitlab.com/pollonegro/pyscap ) @tinoloni is also a contributor there
• https://github.com/sdelafond/debian-oval/tree/master/oval/parser seems to have a parser / emitter for oval and DSA by @sdelafond but seems to be GPL-licensed and may not be usable here
• https://github.com/ComplianceAsCode/content/tree/master/ssg seems to have some Python code
• https://github.com/ribeiroit/python-oval is Python and Apache-licensed by @ribeiroit
• https://github.com/Sep0lkit/oval-for-el by @Sep0lkit seems related and https://github.com/Sep0lkit/oval-for-el/blob/master/scripts/rh2el.py ... but there is no license
• https://github.com/kings-way/OVAL2DB is GPL
• https://github.com/oholiab/ovaltools by @oholiab is Python and BSD-licensed
• https://github.com/sandabuliu/ovalparser by @sandabuliu is Pyton but has no license

[sdelafond]

debian-oval is indeed GPL.

[oholiab]

ovaltools is pretty proof-of-concept and very heavily based around Ubuntu's OVAL files - basically being able to map from a list of package versions to a list of vulnerabilities. I don't doubt there are many more mature solutions out there but I'm certainly interested to see what solutions you come up with!

[sbs2001]

This can be closed, but I believe we could stretch this a bit instead of creating a new ticket . Instead of having SUSEOvalParser UbuntuOvalParser etc, we could have just one OvalParser to parse them all.

Criteria to close this issue :
Replace SUSEOvalParser and UbuntuOvalParser with OvalParser and pass all the existing tests.