Added missing text for english and new texts in english and spanish.
Cambios para hacer commit:
modificado: app/assets/stylesheets/participation.scss
modificado: app/models/concerns/imageable.rb
modificado: app/models/poll.rb
modificado: app/views/admin/poll/polls/_form.html.erb
modificado: app/views/images/_admin_image.html.erb
modificado: config/locales/en/images.yml
modificado: config/locales/es/admin.yml
modificado: config/locales/es/images.yml
modificado: spec/features/admin/poll/polls_spec.rb