* Rename "Credentials" page to "Security" for clarity

* Change "security" icon from cog to lock

Also domain_block fabricator now sets unique domains

* more free pgconfig for streaming by .env

* fix wrong default values

* database.yml read ENV as same as streaming server

* Add overview of active sessions

* Better display of browser/platform name

* Improve how browser information is stored and displayed for sessions overview

* Fix test

Setting ASSET_HOST to `http://0.0.0.0:8080` makes urls in manifest.json to
be invalid, e.g. `http://0.0.0.0:8080/packs/application.js`.

Anyway, we don't need set this on build:development because assets would
be delivered from same origin in development (and w/o dev-server).

Webpack seems to fail to import `react-intl/locale-data/*.js` if those
files has been proceed by babel, and this also breaks applying our translation.

Note that this won't be a problem on English locale, because react-intl
includes it as default and works fine without manually added locale-data.
Also this issue seems to only occurs on production build, but I'm not sure
about reason.

User-controlled multi-column/single-column overrides

* Remove unused column_collapsable.js
* Remove old styles
* Extract `> div`  style to independent class

Avatars now have consistent styling across all pages; border radius can be adjusted with a SASS variable ($ui-avatar-border-size)