Sometimes we would like to create a base image without any DB access, this
assists in creating custom base images with custom plugins that already
includes `public/assets`
Following this change set you can run:
```
SPROCKETS_CONCURRENT=1 DONT_PRECOMPILE_CSS=1 SKIP_DB_AND_REDIS=1 RAILS_ENV=production bin/rake assets:precompile
```
Then it is straight forward to create a base image without needing a DB or
Redis.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
* Feature: Push notifications for Android
Notification config for desktop and mobile are merged.
Desktop notifications stay as they are for desktop views.
If mobile mode, push notifications are enabled.
Added push notification subscriptions in their own table, rather than through
custom fields.
Notification banner prompts appear for both mobile and desktop when enabled.
