allow to edit GroupOrderArticle result from orders screen

Conflicts:
	app/assets/javascripts/application.js

app/inputs/delta_input.rb

@@ -0,0 +1,24 @@
+# encoding: utf-8
+
+class DeltaInput < SimpleForm::Inputs::StringInput
+  # for now, need to pass id or it won't work
+  def input
+    @input_html_options[:data] ||= {}
+    @input_html_options[:data][:delta] ||= 1
+    @input_html_options[:autocomplete] ||= 'off'
+    # TODO get generated id, don't know how yet - `add_default_name_and_id_for_value` might be an option
+
+    template.content_tag :div, class: 'delta-input input-prepend input-append' do
+      delta_button('−', -1) + super + delta_button('+', 1)
+    end
+  end
+  #template.button_tag('−', type: :submit, data: {decrement: @input_html_options[:id]}, tabindex: -1, class: 'btn') +
+
+  private
+
+  def delta_button(title, direction)
+    data = { (direction>0 ? 'increment' : 'decrement') => @input_html_options[:id] }
+    delta = direction * @input_html_options[:data][:delta]
+    template.button_tag(title, type: :button, name: 'delta', value: delta, data: data, tabindex: -1, class: 'btn')
+  end
+end