Adding a welcoming page prompting to add a Provider

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1678190

app/views/ems_infra/_empty.html.haml

@@ -0,0 +1,18 @@
+.blank-slate-pf
+  .blank-slate-pf-icon
+    %span.pficon.pficon-add-circle-o
+  %h1= _("Add a Provider")
+  %p
+    = _("You don't have any providers to display. Please add a Provider.")
+  %p
+    = _("Learn more about this")
+    %a{:href => "https://manageiq.org/docs/get-started/add-a-provider"}
+      = _("in the documentation.")
+  .blank-slate-pf-main-action
+    = link_to(_('Add a Provider'),
+      {:action => 'new'},
+      :class => 'btn btn-primary btn-lg',
+      "data-miq_sparkle_on" => true,
+      "data-miq_sparkle_off" => true,
+      "data-method" => :post,
+      :title => _("Add a new Infrastructure Provider"))

app/views/ems_infra/show_list.html.haml

@@ -1,2 +1,5 @@
 #main_div
-  = render :partial => 'layouts/gtl'
+  - if ExtManagementSystem.any?
+    = render :partial => 'layouts/gtl'
+  - else
+    = render :partial => 'empty'

config/routes.rb

@@ -1296,6 +1296,7 @@
         tagging_edit
       ),
       :post => %w(
+        new
         button
         create
         form_field_changed