Add config option to disable the invites

Some foodcoops require that an admin adds all users to have more control
over the users.

app/views/admin/configs/_tab_others.html.haml

@@ -2,5 +2,6 @@
   = config_input form, :use_wiki, as: :boolean
 = config_input form, :use_nick, as: :boolean
 = config_input form, :tolerance_is_costly, as: :boolean
+= config_input form, :disable_invite, as: :boolean
 = config_input form, :help_url, as: :url, input_html: {class: 'input-xlarge'}
 = config_input form, :webstats_tracking_code, as: :text, input_html: {class: 'input-xxlarge', rows: 3}

app/views/admin/ordergroups/_form.html.haml

@@ -1,4 +1,4 @@
-- unless @ordergroup.new_record?
+- unless @ordergroup.new_record? || FoodsoftConfig[:disable_invite]
   %p= t('.first_paragraph', url: link_to(t('.here'), new_invite_path(id: @ordergroup.id), remote: true)).html_safe
 = simple_form_for [:admin, @ordergroup] do |f|
   - captured = capture do

app/views/admin/workgroups/_form.html.haml

@@ -1,4 +1,5 @@
-%p= t('.first_paragraph', url: link_to(t('.here'), new_invite_path(id: @workgroup.id), remote: true)).html_safe
+- unless FoodsoftConfig[:disable_invite]
+  %p= t('.first_paragraph', url: link_to(t('.here'), new_invite_path(id: @workgroup.id), remote: true)).html_safe
 = simple_form_for [:admin, @workgroup] do |f|
   - captured = capture do
     %h4= t 'admin.access_to'