Changes to user registration form and inventories

Registration form: Subclassing UserCreationForm for easy addition of
password confirmation.
views: Changing field name to match first and second password fields.
models: making the year integer field an html select box with named
values to avoid confusion.
Index, inventories.view, base: Removing references to the inventories
page until such time as we can decide what to do with it.
Merge branch 'erich_dev'