add ability to flag people/pubs

[mmckegg]

Let's say that patchwork goes viral and we get a bunch of miserable junk on the network. Someone might want to block the pub that onboarded those people. Flagging would handle that quite nicely. We should add it back into the interface.

I'd feel much better about "public" pubs if flagging was an easy option.

[mmckegg]

Added block feature a few commits ago! Closing!