Ssh key table

https://bugzilla.novell.com/show_bug.cgi?id=859074

Instead of using a textarea, use the dynamicTable plugin. The only issue is, that it relies on some sort of unique IDs to work properly (e.g node-names) and there's nothing similar for the case of ssh keys. We can still use md5 checksums as those (https://github.com/crowbar/barclamp-crowbar/pull/1073), stored in a hidden field (https://github.com/crowbar/barclamp-crowbar/pull/1072).

The patch is missing:

1) Update to schema
2) Migration

If anyone would be willing to help me w/ those, that'd be great.