Allow users to import via Liquid username, email as well as Twitter

[dallasjc]

Add additional options for users to identify author when importing legislation modeled after the proxy-search form

This pr builds on this pr: https://github.com/voteliquid/liquid.us/pull/187

• [ ] by Liquid username

 I’ve gotten this working by setting a cookie for author_id and author_username

• [x] by Twitter username

• [ ] by email

  • [x] create username field
  • [x] create name field
  • [x] create user image link field
  • [ ] activate new fields after added to backend

• [x] modify importVote function to allow for email and Liquid

• [ ] Set up Liquid searches so the results are imported directly

• [x] set up separate importViaEmail function currently uses the same rpc/import-vote function, may have to change this