Allow blank votes in polls via web

With the old interface, there wasn't a clear way to send a blank ballot.
But now that we've got a form, there's an easy way: clicking on "Vote"
while leaving the form blank.

config/locales/en/general.yml

@@ -604,6 +604,7 @@ en:
     show:
       already_voted_in_booth: "You have already participated in a physical booth. You can not participate again."
       already_voted_in_web: "You have already participated in this poll. If you vote again it will be overwritten."
+      already_voted_blank_in_web: "You have already participated in this poll by casting a blank vote. If you vote again it will be overwritten."
       back: Back to voting
       cant_answer_not_logged_in: "You must %{signin} or %{signup} to participate."
       comments_tab: Comments

config/locales/en/responders.yml

@@ -11,6 +11,7 @@ en:
         poll_question_option_video: "Video created successfully"
         poll_question_option_image: "Image uploaded successfully"
         poll_voter: "Thank you for voting!"
+        poll_voter_blank: "Thank you for voting! Your vote has been registered as a blank vote."
         proposal: "Proposal created successfully."
         proposal_notification: "Your message has been sent correctly."
         budget_investment: "Budget Investment created successfully."

config/locales/es/general.yml

@@ -604,6 +604,7 @@ es:
     show:
       already_voted_in_booth: "Ya has participado en esta votación en urnas presenciales, no puedes volver a participar."
       already_voted_in_web: "Ya has participado en esta votación. Si vuelves a votar se sobreescribirá tu resultado anterior."
+      already_voted_blank_in_web: "Ya has participado en esta votación mediante un voto en blanco. Si vuelves a votar se sobreescribirá tu resultado anterior."
       back: Volver a votaciones
       cant_answer_not_logged_in: "Necesitas %{signin} o %{signup} para participar."
       comments_tab: Comentarios

config/locales/es/responders.yml

@@ -11,6 +11,7 @@ es:
         poll_question_option_video: "Vídeo creado correctamente"
         poll_question_option_image: "Imagen cargada correctamente"
         poll_voter: "¡Gracias por votar!"
+        poll_voter_blank: "¡Gracias por votar! Tu voto se ha contabilizado como en blanco."
         proposal: "Propuesta creada correctamente."
         proposal_notification: "Tu mensaje ha sido enviado correctamente."
         budget_investment: "Proyecto de gasto creado correctamente."