Add bio fields (#6645)

* Add bio fields

- Fix #3211
- Fix #232
- Fix #121

* Display bio fields in web UI

* Fix output of links and missing fields

* Federate bio fields over ActivityPub as PropertyValue

* Improve how the fields are stored, add to Edit profile form

* Add rel=me to links in fields

Fix #121

db/migrate/20180410204633_add_fields_to_accounts.rb

@@ -0,0 +1,5 @@
+class AddFieldsToAccounts < ActiveRecord::Migration[5.1]
+  def change
+    add_column :accounts, :fields, :jsonb
+  end
+end