Add DEFAULT_FROM_EMAIL = SERVER_EMAIL in settings/common.py

[Peter Bittner]

User Story

As a website admin / developer I want the value DEFAULT_FROM_EMAIL be set to SERVER_EMAIL by default so that emails don't come from webmaster@localhost by default (which lands in SPAM folders).

Acceptance Criteria

• We know whether we need this setting in any function we're using with django-Organice (e.g. does django-allauth honor the setting?)
• DEFAULT_FROM_EMAIL is set in a newly generated django-Organice instance

[Peter Bittner]

Fixed with commit 1f45d6e.