Inventory for custom

Part 1: Setting of two basic pages, the list of items and the list of tags

      linked to pages detailing of each item and tag.
      The main fields of the model Item are name, description, quantity,
      entry_date, slug.
      Assuming the data base filled with information, we would like to add
      another field 'estimated_price' without damaging the existing 
      database. The option is to set the new field in the directory 
      migrations.

Part 2: Adding of the field total_item_estimated_price for each item depending

      on its quantity.
      In views.py:
      Use of queryset expressions to update the field total_item_estimated_price
      and to estimate the total_inventory_value by summing the column of the field
      total_item_estimated_price.

Part 3: Adding of the choice of currencies (EURO, USD, CAD).

      Adding of the update of the currency of the whole items and the total_inventory_value
      if one currency is changed.