Integrate Zeno as an alternative crawler

[machawk1]

https://github.com/internetarchive/Zeno

[machawk1]

It appears that the project moved from Apache to GPL license since this issue was filed yesterday. We really ought to do a sanity check of the licenses of the other embedded tools.

EDIT: rrrroyal "we"

• MemGator: MIT
• OpenWayback: Apache
• Heritrix: Apache

Prior commit 687b5d5982be433206b03022d0a03dc0a1227501 of Zeno maintains an Apache license.