Account namespace updates: part 4 (transfers, singular namespacing) (#896)

* Move Transfer to Account namespace

* Fix partial resolution due to namespacing plurality

* Make category and tag controllers consistent with namespacing convention

* Update stale partial reference

app/controllers/category/deletions_controller.rb

@@ -0,0 +1,26 @@
+class Category::DeletionsController < ApplicationController
+  layout "with_sidebar"
+
+  before_action :set_category
+  before_action :set_replacement_category, only: :create
+
+  def new
+  end
+
+  def create
+    @category.replace_and_destroy! @replacement_category
+
+    redirect_back_or_to transactions_path, notice: t(".success")
+  end
+
+  private
+    def set_category
+      @category = Current.family.categories.find(params[:category_id])
+    end
+
+    def set_replacement_category
+      if params[:replacement_category_id].present?
+        @replacement_category = Current.family.categories.find(params[:replacement_category_id])
+      end
+    end
+end