Merge pull request #1074 in SNORT/snort3 from json_update to master

Merge pull request #1074 in SNORT/snort3 from json_update to master

Squashed commit of the following:

commit b77eea3ec6a9545d4ca359b1586467cfd4ebcd9f
Author: Russ Combs (rucombs) <rucombs@cisco.com>
Date:   Tue Nov 21 08:33:22 2017 -0500

    snort2lua: tweak const name for clarity (internal)

commit 714bb45f048ba47c0ad766edec21ab6813bc78fd
Author: Russ Combs (rucombs) <rucombs@cisco.com>
Date:   Tue Nov 21 07:45:22 2017 -0500

    rules: default msg = "no msg in rule"

commit 9eba78b7f2d3bb4e89fba2b2f0fb95beb754857f
Author: Russ Combs (rucombs) <rucombs@cisco.com>
Date:   Tue Nov 21 07:44:00 2017 -0500

    alert_csv: various fixes to match alert_json

    eth_len: changed to decimal format
    msg: remove extra quotes
    seconds: new decimal field for unix-style timestamp

commit 2244c7d12ceb18e93aaa7ed449e134a42e1eb3fc
Author: Russ Combs (rucombs) <rucombs@cisco.com>
Date:   Tue Nov 21 07:40:30 2017 -0500

    alert_json: various fixes; thanks to Noah Dietrich <noah_dietrich@86penny.org> for reporting the issues

    eth_len: changed to decimal format
    eth_type: changed to string format (hex value)
    msg: remove extra quotes
    seconds: new decimal field for unix-style timestamp