Merging Bhavesh Goyal's improvement to the mass subscription email validation

Merging Ankush Sharma's fix so that mass subscription is available to list owner and superuser, not to list moderators.

Switched else to another except. This was causing a test failure in test_confirmation_link (postorius.tests.test_address_activation.TestAddressConfirmationProfile); all tests now pass.

The Mass Subscription option is a power of List owner not of List moderator.

Merging Ankush Sharma's fix for Bug #1428543

Merging Abhilash Raj's fix for Bug #1437866 (and a duplicate #1430682)

remove the contact address on domain list page to fix the error for meanwhile

Merging Bhavesh Goyal's fix for Bug #1431474 (with one change to the mass subscribe access)

Merging Pavan Koli's fix for Bug #1436309

* Fallback from EMAIL_CONFIRMATION_FROM to DEFAULT_EMAIL_FROM ...

* Raise ImproperlyConfigured if both of them are not defined
* Remove whitespaces

removed old unused view module

django_browserid init: use included JS script instead of making the method call in the page.

Fixed Invalid Email Acceptance in Mass Subscription

Fixed method decorators which caused Bug #1435062

Typos fixed

feature-implemented-mass-removal

Fixed Bug #1431474 postorius user nav role fix

adding dropdown option for pipeline

Merge changes

Feature Added: Mass Removal for List Members

Fix manage.py mmclient command for non-IPython shells. Contributed by Ankush Sharma (LP: 1428169).

Mozilla Persona integration: switch from django-social-auto to django-browserid: Contributed by Abhilash Raj.

replace django-social-auth with django-browserid

Fixed #1428543.

Way for a list administrator/owner to easily export a CSV of current subscribers.

Fixed the issue #1428169.

removed unnecessary installation instruction from dev docs

* added tox to dev dependencies ...

* removed duplicate dependency file
* dev docs text change

small text change in dev docs

dev docs: note added