amo/monitors: don't error on twemproxy.

Don't error if there is only one memcached server configured and that
server is 127.0.0.1.
devhub tracking WIP
Fixed payment account in search api (bug 958604)
Added stats and revenue_stats perms to account api.
Since the transition to DRF we don't need to alter ._view_name

SearchView and FeaturedView are already differenciated correctly.
Updated translation for messages.po

Added missing translation and fixed existing ones
Missing comma
Add back update_developer_name command temporarily

(30 or so public apps have no developer_name set, they must have been
 had some issues when the command was ran, add it back so that we can
 fix them)
Merge pull request #1623 from diox/add-back-update_developer_name

Add back update_developer_name command temporarily
Create FeedApp model (+ docs, API endpoints) to feature individual apps in feed (bug 937338)
Ensure that SplitField output and input fields receive the parent field's context
API performance tweaks regarding apps (bug 956987)

- Re-use categories instead of using a new queryset
- Re-use all_previews cached list
- Don't load translations when loading versions
- Use a simplified serializer everywhere
- Check premium status before returning prices
Merge pull request #1528 from chuckharmston/937338-feed_featured_app

Create FeedApp model (+ docs, API endpoints) to feature individual apps in feed (bug 937338)
Fix migration number conflict.
Fixes tests broken by 8ee06d3
Merge pull request #1624 from diox/simple-apps-in-api-performance

API performance tweaks regarding apps (bug 956987)
has_premium() is a better check, it will check type first (bug 956987)
Add back invalid category check on write
Fix tests following 3dd2f3e
Add content ratings docs to API docs TOC (bug 959293)