Add extra information to models
Add extra information to models

Add Votetaker.pgpkey
Election.shortname is optional as legacy elections don't have it
Election.votetaker and .proposal are optional as newly-created elections
might not have them
Index Statement by (release_date, slug)
Index Election by (status, result_date)
Add url methods to Statement and Election

jribbens/voting,jribbens/voting