severity and cvss metrics support

[chen-keinan]

This change is about supporting severity, CVSS v2, and v3 metrics (if exist)

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[gopherbot]

This PR (HEAD: 8503ad33ebc2046af80262d2f687e9ad92ae8b26) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/vulndb/+/330089 to see it.

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[gopherbot]

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Patch Set 1:

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[gopherbot]

This PR (HEAD: 4d4b7f4e88d7571d73676b0724b003e6e2f8b3d8) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/vulndb/+/330089 to see it.

Tip: You can toggle comments from me using the comments slash command (e.g. /comments off) See the Wiki page for more info

[gopherbot]

This PR (HEAD: a9995153cc660ad89299fd69d5801a836a098df7) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/vulndb/+/330089 to see it.

Tip: You can toggle comments from me using the comments slash command (e.g. /comments off) See the Wiki page for more info