Add main link to each phase of the budget

Co-authored-by: decabeza <alberto@decabeza.es>

db/migrate/20200309112812_add_main_link_to_budget_phases.rb

@@ -0,0 +1,6 @@
+class AddMainLinkToBudgetPhases < ActiveRecord::Migration[5.0]
+  def change
+    add_column :budget_phase_translations, :main_link_text, :string
+    add_column :budget_phases, :main_link_url, :string
+  end
+end