gnu-social/plugins/Poll

Unfinished basic stuff:
* make pretty graphs for response counts
* ActivityStreams output of poll data is temporary; the interfaces need more flexibility
* ActivityStreams input not done yet
* need link -> show results in addition to showing results if you already voted
* way to change/cancel your vote

Known issues:
* HTTP caching needs fixing on show-poll; may show you old data if you voted after

Things todo:
* should we allow anonymous responses? or ways for remote profiles to respond locally?

Fancier things todo:
* make sure backup/restore work
* make sure ostatus transfer works
* a way to do poll responses over ostatus directly?
* allow links, tags, @-references in poll question & answers? or not?

Storage todo:
* probably separate the options into a table instead of squishing them in a text blob