Fixing is_imported flag to indicate upstream translations

Basically:

• is_current -> is_current_in_ubuntu

• is_imported -> is_current_upstream

Implementation

• Rename is_current/is_imported flags to is_current_ubuntu/is_current_upstream (cleanup)

• Rename is_published to from_upstream on TranslationImportQueue (cleanup)

• Change 'changed in Launchpad' terminology to be 'changed in Ubuntu'
• Remove reference to 'published' uploads from the UI (cleanup)
• Change terminology in ExistingPOFileInDatabase (cleanup)
• updateTranslation cleanup and changes
  • Find exact same translationmessage
  • Privilege checks for updateTranslation replacement calls
  • Sanitization and validation code into utility
  • submitSuggestion
  • Clearing/unsetting translations
  • Dismiss suggestions

  • setCurrentTranslation

  • Diverge translation
  • Replace updateTranslation calls with calls to new methods
• Adapt UI to work with new flags and new semantics for upstream projects
• Translations overview pages for projects (statistics update)

• POFile:+translate filters

• Privileges for updateTranslation
• Migration script: set is_current_upstream from is_current_ubuntu flag on upstream projects, clear is_current_ubuntu if there is no link
• Update message-sharing-merge script for the new semantics
• Fix up gettext-check-messages script to be symmetric for is_current_upstream and is_current_ubuntu flags
• Enable sharing between templates in products and Ubuntu