Merge pull request #2892 from HyphaApp/feature/gh-2812-in-app-notifications

hypha/apply/activity/context_processors.py

hypha/apply/activity/filters.py

hypha/apply/activity/models.py

...ty/templates/activity/include/notifications_dropdown.html

hypha/apply/activity/templates/activity/notifications.html

hypha/apply/activity/templatetags/activity_tags.py

hypha/apply/activity/urls.py

hypha/apply/activity/views.py

hypha/settings/base.py

hypha/static_src/src/javascript/apply/notifications.js

...rc/src/sass/apply/components/_activity-notifications.scss

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

hypha/static_src/src/sass/apply/main.scss

hypha/templates/base-apply.html

hypha/templates/includes/sprites.html