feat(syslog): add all CVSS scores/vectors

[knqyf263]

What did you implement:

Add all CVSS scores (NVD, JVN, RedHat, etc.)

How did you implement it:

Iterate all CveContents

How can we verify it:

$ vuls report -to-syslog

$ nc -l 514
<129>2018-06-06T20:44:11+09:00 MBP vuls[77805]: scanned_at="2018-06-06 16:19:18.923111854 +0900 JST" server_name="debian8" os_family="debian" os_release="8.10" ipv4_addr="10.0.2.15,192.168.33.11" ipv6_addr="" packages="linux-image-3.16.0-4-amd64" cve_id="CVE-2018-5750" cvss_score_nvd_v2="2.10" cvss_vector_nvd_v2="AV:L/AC:L/Au:N/C:P/I:N/A:N" cwe_id="CWE-200" source_link="https://nvd.nist.gov/vuln/detail/CVE-2018-5750" summary="The acpi_smbus_hc_add function in drivers/acpi/sbshc.c in the Linux kernel through 4.14.15 allows local users to obtain sensitive address information by reading dmesg data from an SBS HC printk call."

Todos:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[kotakanbe]

LGTM