Display all languages (both active and inactive) on smartling settings

Bugreport from p...com

Problem/Motivation

We cannot send content for translation for disabled locales. We want to start translation for new locales but we don't want to display uncompleted locales on site
Steps:

1. Add >2 languages on site
   
2. Smartling displays all languages except the original
   
3. Disable one of language
   
4. Look at smartling settings and bulk submit. They don't contain disabled languages
    

Proposed resolution

Smartling translation can work even if language is disabled. Let's not block translation in such cases

Remaining tasks

1. Smartling settings displays all languages (both active and inactive)
2. User can configure languages mappings for active and inactive languages
3. Bulk submit also contains all languages
4. We don't loose settings of disabled languages after saving settings
5. Add a test for downloading translation for disable language

@Soul88, pls commit fix in 2.x, not in oop