Groups and headings CRUD from budget view

Before, users needed to navigate to the list of groups in order to
add, edit or delete a group.

Also, they need to navigate to the list of groups first, and then to
the list of headings for that group in order to add, edit or delete a
heading.

Now, it's possible to do all these actions for any group or heading
from the participatory budget view to bring simplicity and to reduce
the number of clicks from a user perspective.

Co-Authored-By: Javi Martín <javim@elretirao.net>

config/routes/admin.rb

@@ -57,8 +57,8 @@ namespace :admin do
       put :calculate_winners
     end
 
-    resources :groups, except: [:show], controller: "budget_groups" do
-      resources :headings, except: [:show], controller: "budget_headings"
+    resources :groups, except: [:index, :show], controller: "budget_groups" do
+      resources :headings, except: [:index, :show], controller: "budget_headings"
     end
 
     resources :budget_investments, only: [:index, :show, :edit, :update] do