Make versions of functions that do not depend on a phoenix form

[bryanjos]

Right now we can do this

<%= form_for @changeset, @route, fn f -> %>
  <%= row do %>
    <%= col medium: 6 do %>
      <%= text_input_stack f, :amount, label: gettext("Name"), input: [placeholder: gettext("Name"), required: true] %>
    <% end %>
    <%= col medium: 6 do %>
      <%= text_input_stack f, :reference_number, label: gettext("Number"), input: [placeholder: gettext("Number"), required: true] %>
    <% end %>
  <% end %>
<% end %>

but not

<%= form_tag("/hello", method: "get") do %>
  <%= row do %>
    <%= col medium: 6 do %>
      <%= text_input_stack :amount, label: gettext("Name"), input: [placeholder: gettext("Name"), required: true] %>
    <% end %>
    <%= col medium: 6 do %>
      <%= text_input_stack :reference_number, label: gettext("Number"), input: [placeholder: gettext("Number"), required: true] %>
    <% end %>
  <% end %>
<% end %>