Make the composer and TopicCreator use category id instead of category name

Also fixes #1171
Added backwards compatibility for topic creation
Extracted nickname registration into a private controller method
Added strings

Added some strings not yet existing in the "es" locale but already in use in the application.
Extract ListController#list_target_user
improved specs for avatar
add a warning whenever the uploaded image is not a square
Lower Complexity of UsersController
https://codeclimate.com/github/discourse/discourse/UsersController#method-complexity
Russian translation (actual version)
Merge pull request #1375 from versvs/master

Added strings
Merge pull request #1379 from abbat/master

Russian translation (actual version)
Merge pull request #1376 from gcapizzi/lists_controller_refactoring

ListController refactoring
Merge pull request #1371 from einarj/cleanup_user_registration

Extracted nickname registration into a private controller method
Merge pull request #1377 from ZogStriP/avatar-work

Improved specs for avatar + added a warning whenever the uploaded image is not a square
FIX: changing another user's avatar changes yours
Merge pull request #1380 from ZogStriP/fix-changing-another-user-avatar-changes-your-not-theirs

FIX: changing another user's avatar changes yours
Added test case for nickname registration failure

* Also made a minor readability change by moving the auth.present? check
* from UsersController#create into #create_third_party_auth_records
* which is the method that relies on the check.
No more rails 4 deprecation warnings
add max_image_height site setting
Merge pull request #1382 from novemberkilo/master

No more rails 4 deprecation warnings