[DJ1.10] Update election_urls to have names and be reversed by name

helios/election_url_names.py

helios/election_urls.py

helios/templates/_castconfirm_docast.html

helios/templates/_castconfirm_password.html

helios/templates/cast_done.html

helios/templates/castvote.html

helios/templates/combine_decryptions.html

helios/templates/election_audited_ballots.html

helios/templates/election_bboard.html

helios/templates/election_build.html

helios/templates/election_cast_confirm.html

helios/templates/election_compute_tally.html

helios/templates/election_edit.html

helios/templates/election_extend.html

helios/templates/election_freeze.html

helios/templates/election_keygenerator.html

helios/templates/election_not_started.html

helios/templates/election_questions.html

helios/templates/election_register.html

helios/templates/election_tallied.html