Merge pull request #517 from OpenTechFund/feature/299-improve-activity-rendering

opentech/apply/activity/messaging.py

...ivity/migrations/0012_add_generic_relation_to_activity.py

opentech/apply/activity/models.py

opentech/apply/activity/options.py

...ply/activity/templates/activity/include/listing_base.html

opentech/apply/activity/templatetags/__init__.py

opentech/apply/activity/templatetags/activity_tags.py

opentech/apply/activity/tests/test_messaging.py

opentech/apply/activity/views.py

opentech/apply/determinations/views.py

opentech/apply/funds/models/submissions.py

opentech/apply/funds/views.py

opentech/apply/review/models.py

opentech/apply/review/views.py

opentech/static_src/src/sass/apply/components/_feed.scss