Support single redis DB.
Various cleanups to Ubuntu installation instructions:

* Avoid editing /etc/apt/sources.list add nginx repo, instead create
  /etc/apt/sources.list.d/nginx.list

* Avoid editing /etc/nginx/nginx.conf, instead put server_name_hash_buckets
  setting into discourse.conf

* Proper-case Discourse when it is referring to the product name, so that all
  the lowercase references are to the user created during the installation
Address @Supermathie's concerns in PR1430
Locate the Puma config file.
Update puma.rb
Don't show "uncategorized" if allow_uncategorized_topics is false.
Updated Swedish client translations
Support for "no subcategories"
Merge pull request #1740 from davh/master

Updated Swedish client translations
Merge pull request #1739 from vikhyat/uncategorized-topics

Don't show "uncategorized" in the category dropdown if allow_uncategorized_topics is false.
FIX: Large `pre` blocks in emails were increasing the width.
Allow categories with null position, which means sort them based on activity. Mix absolutely positioned (position is not null) categories with null position categories.
FIX: text node emitters should always take strings as parameters even if they
return JsonML.
Russian translation (actual version)
Improve spacing of registration form, and add instructions to the password field.
FIX: canonical url should not use the CDN
FEATURE: default_code_lang for syntax highlighting is configurable
missing site setting, this should be auto generated
fix spec, categories without position are now always at the end of the list
Admin Quick Start Guide: Change email test link

The feature has moved from `/admin/email/logs` to `/admin/email`.