Time Tracking should take other indexing language into account

At the moment, Time Tracking doesn't account for indexing in languages other than English.

Steps to reproduce

1. Change Default language in General Configuration to français (France) or Language Preference in Profile to français (France)
2. Change indexing language to french.
3. Disable Time Tracking.
4. Set time format to jours
   
5. View an issue. Time Tracking should be shown like this:
   
6. Edit the issue
7. Use 'j' instead of 'd'. This error will be prompted:
   

Affected processes

• Issue cannot be edited if the value is entered as 'j'
• REST API will fail with this error:

  {
      "errorMessages": [],
      "errors": {
          "timetracking_originalestimate": "L'estimation originale spécifiée n'est pas valide."
      }
  }
  

Expected behavior
original estimate or remaining estimate should read 'j' as 'd'