Extended status/health checks

[taam]

Without further knowledge of the intended scope of this script, here are some ideas for additional checks regarding the health of the zpools:

• scrub status (there exists a project that does that already as shell script: https://github.com/Josef-Friedrich/check_zpool_scrub)
• disk status
• disk error counts (READ/WRITE/CKSUM)
• data errors

So basically it would be nice to get a warning if zpool status shows anything unusual. (I admit that might be hard to generalize, I think I try a simple regex solution first.)