Use number fields to enter number of votes

This way the fields are easier to use, and we can get rid of the
placeholders.

Note we're simplifying the `answer_result_value` in order to make it
easier to return `0` instead of `nil` when the field is empty.

Also note there's a small change of behavior here; previously, these
fields were empty by default, and now their value is `0` by default, so
blindly clicking the "Save" button would send `0` instead of an empty
value. I don't think it's a big deal, though, but we need to keep that
in mind.

spec/components/officing/results/form_component_spec.rb

@@ -0,0 +1,19 @@
+require "rails_helper"
+
+describe Officing::Results::FormComponent do
+  let(:poll) { create(:poll, ends_at: 1.day.ago) }
+  before { create(:poll_question, :yes_no, poll: poll, title: "Agreed?") }
+
+  it "uses number fields with 0 as a default value" do
+    render_inline Officing::Results::FormComponent.new(poll, Poll::OfficerAssignment.none)
+
+    page.find(:fieldset, "Agreed?") do |fieldset|
+      expect(fieldset).to have_field "Yes", with: 0, type: :number
+      expect(fieldset).to have_field "No", with: 0, type: :number
+    end
+
+    expect(page).to have_field "Totally blank ballots", with: 0, type: :number
+    expect(page).to have_field "Invalid ballots", with: 0, type: :number
+    expect(page).to have_field "Valid ballots", with: 0, type: :number
+  end
+end