Delete packages using the management interface

[cpina]

Currently data managers cannot delete created packages using the "management" interface (where data managers use as a day to day tool).

To delete a package it's needed to use the Django admin (see documentation https://github.com/frictionlessdata/schema-collaboration/blob/master/documentation/User.md#admin-access-and-operations)

It might be good (to be discussed) to add an option to delete datapackages in the management.