Lldpd updates and GUI (luci-app-lldpd)

lldpd is just about ready for a GUI but needs one more fix to land in master (and get picked to 23+22).

If you're on github, go ahead and give your approval on these PRs ( -> Files Changed -> Review -> Approve ). Great if you can also test.

The GUI is waiting here, but I have a stack of bug-fixes to go in on top of that.

@marek22 was the original inspiration to port this luci app over.