[#4410] Replace Payment Terms with an Enumeration

Instead of using a hard coded value for Payment Terms, they will use
Redmine's Enumeration table.  This provides an admin gui to managing
the value as well as ordering them.

app/views/contracts/_form.html.erb

@@ -18,7 +18,7 @@
 <% end %>
 
 <% form.inputs :name => l(:text_account_legend) do %>
-  <%= form.input :payment_terms, :as => :select, :collection => resource.payment_terms_for_select %>
+  <%= form.input :payment_term %>
   <%= form.input :po_number %>
   <%= form.input :client_ap_contact_information, :input_html => {:class => 'wiki-edit', :rows => '5'} %>
   <%= form.input :client_point_of_contact, :input_html => {:class => 'wiki-edit', :rows => '5'} %>

app/views/contracts/show.html.erb

@@ -33,7 +33,7 @@
           <%= show_field(resource, :client_point_of_contact, :format => :textilizable, :raw => true, :html_options => {:class => 'contract-client-point-of-contact padd'}, :label_html_options => {:width => '25%'}) %>
           <%= show_field(resource, :executed, :html_options => {:class => 'contract-executed'}) %>
           <%= show_field(resource, :discount_note, :format => :textilizable, :raw => true, :html_options => {:class => 'contract-discount-note'}) %>
-          <%= show_field(resource, :payment_terms, :format => :format_payment_terms, :html_options => {:class => 'contract-payment-terms'}) %>
+          <%= show_field(resource, :payment_term, :format => :format_payment_terms, :html_options => {:class => 'contract-payment-terms'}) %>
           <%= show_field(resource, :client_ap_contact_information, :format => :textilizable, :raw => true, :html_options => {:class => 'contract-client-ap-contact-information'}) %>
           <%= show_field(resource, :po_number, :html_options => {:class => 'contract-po-number'}) %>
           <%= show_field(resource, :details, :format => :textilizable, :raw => true, :html_options => {:class => 'contract-details'}) %>