Refactor Django Upload endpoints to use status field
All file upload viewsets use FileDataSourceViewSet

Allows consistent ordering/filtering for each view
Update django translation strings
Add upload-statuses endpoint
Fix tests after refactor
Refactor pollingUpload directive and fix Upload view

Moves polling upload directive to transitIndicators
so it can make use of OTIUploadStatus

Adds watch on upload

Directive properly detects changes to the passed upload
on page load.
Refactor settings views to use new status messages
Update django translations
Post rebase cleanup: settings-service notes + formatting

Fix django/angular tests
Merge pull request #223 from WorldBank-Transport/feature/api-upload-refactor

Feature/api upload refactor