[#1061] Convert /manage/circle, /community/join /community/leave

* merges them into one page (/circle/USERNAME/edit)

* changes can_trust/can_watch to check for deleted status (consistent
  with old manage/circle/add page

* bonus redesign

Fixes #1061.
[#1061] Redirect old pages to /circle/add

* old pages are: /manage/circle/add, /community/join, /community/leave

* also updates site-generated links

* tweaks DW::Routing->register_redirect to accept a function
  (convenience)
[#1061] Add back /community/join.bml.text (strings still used)
[#1061] Expand filters if action=edge.type

Redirecting from /manage/circle/add sometimes gives us a specific action
(indicating whether the user is more interested in subscribing or giving
access); so we expand the relevant filter section in that case, even if
the user hasn't subscribed/given access yet
Merge pull request #1069 from afuna/convert-manage-circle-bug-1061

[#1061] Convert and redesign /manage/circle/add, /community/leave,