Enable to detect vulnerabilities on FreeBSD

[kotakanbe]

• Implement of the remaining parts of Added FreeBSD support. #90 .
• Add test case.
• Don't use bash on FreeBSD BUG: -o pipefail is not work on FreeBSD's /bin/sh. because it isn't bash #91

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I implemented the remaining part of FreeBSD support.
see #98

• Scan vulns on FreeBSD without root privilege.
• Run with csh, sh... on FreeBSD (no need to create a usr with bash login shell)

There is a point to notice.
SSH password auth is not woking on FreeBSD for now.
So if you want to scan FreeBSD, Please create a user with public key auth on target server before scanning.

Jail support hasn't been implemented yet.
Thanks