Refactor: Topic#invite_by_email

Extract Topic#email_already_existas_for? and Topic#grant_permission_to_user
Fix failing spec due to missing variable in extracted method
Add script to install mandatory config files from their .sample version.
Standardize on 'worker' for sidekiq Procfile entry (expected by buildpack).
Copy default production.rb file.
Allow to set SMTP settings via environment variable.
Improve login modal on mobile
Russian translation (actual version)

 * Migrating from crowdin to transifex translation service (free & less bugs)
 * Reformats YML as transifex service do
Pressing enter in username field of login form will submit the form
Allow Youtube onebox with start time. All params are used in the youtube onebox now.
refactors Discourse.Model to bind context to self plus some minor clean-ups
removes unused context binding from Discourse.Site
Russian translation (actual version)

Fix YML numeric keys
Merge pull request #1511 from velesin/site_self_refactoring

removes unused context binding from Discourse.Site
refactors Discourse.Computed to bind context to self
Merge pull request #1510 from velesin/model_refactoring

refactors Discourse.Model
Merge pull request #1508 from abbat/master

Russian translation (actual version)
Refactor: Topic#invite_by_email

Extract Topic#email_already_existas_for? and Topic#grant_permission_to_user
Fix failing spec due to missing variable in extracted method
Merge branch 'refactor-topic-invite-by-email' of github.com:cored/discourse into refactor-topic-invite-by-email
YoutubeOnebox: FIX HTTP-specific URLs

by replacing with protocol-agnostic URLs.
This fixes the mixed-content warning for secure instances of discourse, at least for Youtube